Brian, I understand your frustration. Unfortunately we're not always going to reach a consensus. Please do not take this personally; it's not due to your "brash communication skills" or "purely social things between us." Everyone here wants to see the best dictionary possible, and sometimes we will simply disagree about how that should look.

It's important to bear in mind that this is a volunteer project, and every proposed amendment is a request for someone else's time and effort. We would like to have productive conversations and reach consensus views as often as possible, but you are not entitled to continue a discussion until you are satisfied. I think the time for review on this entry has passed and we are now moving on.

I believe I gave this in the first edit:
sankoku: (顔が)よく似ていること。

This seems to be an idiom in common use that pretty much all Japanese people know (certainly tossed around easily in modern media)
瓜二つ	58995

Adding a Japanese interview response.

@Stephen. I really appreciate the response.  It is reasonable.  I'm know I'm being really anti-social here.  I don't generally feel so strongly about things, but I disagree that my actual complaint, namely that this is an idiom that is likely to be widely misunderstood, has been at all addressed. I know this may just be rejected out of hand too.  I can wait a while for things to cool and then expand this to a general discussion on github about misleading and "dangerous" glosses later.  There may be 200k entries in jmdict, but there probably not more than 500 or 1000 super-commonly understood everyday idioms, and this is appears be one of them. It's worth having accurate glosses.

I was at the local greengrocer today, seemed like a good place to ask about 瓜二つ.  The nice Japanese woman running the shop gave me the the standard answer よく似ています. I asked - イメージだけ？　性格は同じなら... she made a funny face. No no, 顔が似ている, I kid you not, two very-similar little girls were running by outside and she pointed at them, and said "like those twins, they have exactly the same face".  And I said face only?  And she said yes, 顔がよく似ています.  I even explained why I was having the conversation, picked up a package of peas, and told her the English idiom (which she did not know).

If we'd kept an [expl] or a [lit] gloss, the rationale for "esp. the face" (verified by sankoku), would be obvious.

I didn't realize this was going to be such a controversy when I started.  If I had, I would have approached things differently.  When I got here, *peas in a pod* was the only gloss, and it was so strikingly wrong in the context I found it that I put a lot of effort into trying to fix this entry.  And "it's in the JEs", and "the OED defines as..." being given as a rationale to ignore what I know as an English speaker to be incorrect about an English idiom is incredibly disheartening.  I feel like I'm being told I don't understand my own language.

I know my brother doesn't count because he shares the same linguistic upbringing I do, but I had him on the phone and asked about "peas in a pod".  After he described the behavior of twins as an example, I asked "do two people have to look alike to be peas in a pod?".  His answer "appearance has practically nothing to do with it".  How could these idioms be more mismatched than that?

We can all disagree on what any particular idiom means.  That's fine. But whether an idiom is likely to cause confusion is an objective fact.  No one here has disputed the point that "peas in a pod" is likely to cause widespread misunderstandings for anyone who might chose to use it.  I really don't understand what the technical point of resistance is here, other than purely social things between us, and in particular brash communication skills on my part.

I've added my first hand experience with an actual Japanese person for the record.  I'm leaving "like peas in a pod" at the end in the hope you'll approve this edit as part of the main record, and add "esp. the face".  I maintain that it would be better for users of jmdict if "peas" were dropped, but I'll try not to look at this again for a while and let things be, whatever you chose to do.

@@ -21,2 +21 @@
-<gloss>exactly alike (in appearance)</gloss>
-<gloss>like two peas in a pod</gloss>
+<gloss>exactly alike in appearance (esp. the face)</gloss>
@@ -25,0 +25 @@
+<gloss>like peas in a pod</gloss>

gg5: そのふたごは本当にうり二つだ.　Those twins are exactly alike [as alike as two peas in a pod].
prog: 二人は瓜二つだ Those two are 「exactly alike [as like as two peas (in a pod)].
luminous: その双子はうり二つだ The twins are as alike as two peas (in a pod).
wisdom: あの兄弟は瓜二つだ Those brothers are exactly [very much] alike. ｟話｠ Those brothers are as like as two peas (in a pod) [are like two peas in a pod].

I think you've cleared up any potential confusion with the addition of "(in appearance)" to the first gloss.
We have more than enough evidence that "two peas in a pod" is an appropriate gloss for 瓜二つ.

@@ -21,0 +22,2 @@
+<gloss>like two peas in a pod</gloss>
+<gloss>(practically) identical</gloss>
@@ -24 +25,0 @@
-<gloss>(practically) identical</gloss>

https://www.quora.com/What-is-generally-understood-by-the-cliche-like-peas-in-a-pod-when-said-of-people
Peas in a pod from which the the idiom like peas in a pod refers to, are English (garden peas), a type of climbing legume that result in pods that contain a row of visually perfect and almost identical round peas. The idiom itself concludes that the implied (usually two or more people) pair or group display traits, mannerisms, ideas, or habits that are almost indistinguishable. Like peas in a pod says that they are kindred and must have came from the same place in one way or another to be so alike.

https://www.quora.com/What-are-all-the-two-peas-in-a-pod-sayings-and-what-do-they-mean
Answer 1. “Two peas in a pod” - Two things that go together
Ex : Me and my sister are two peas in a pod. We both love to ski, swim, and draw.

Answer 2. Actually it usually refers to two people who are similar in every way ..ie each one like the other ..so that it would seem they come out of the same “pod “.

Answer 3. So then one could say of two siblings that are “the same/like-minded/share the same interests/dress the same/share the same interests and aspirations /have similar character traits or personalities .. or even may even look the same etc., as being “like two peas in a pod”.

https://www.urbandictionary.com/define.php?term=two peas in a pod
two people getting along really well
lani and makayla are like two peas in a pod when theyre together

two peas in a pod
literally 2 biffles who can live in a pod.
In other words, very similar people!

wudgie & budgie
valentine's dae baes 4 ever like two peas in a pod

To be fair (and I don't have this intuition *at all*):
Two people who look almost identical.
Zooey Deschanel and Katy Perry are two peas in a pod!

2 peas in a pod
Very similar, a couple made for each other

again, "like two peas in a pod" ...  I will stipulate that the OED, Cambridge, and Collins definitions all support what this term *used to mean* (and still means to some people), and that it is reasonable for older J-E references to have incorporated it. 

I like pointing at dictionaries as much as the next person.  In fact I did as much, pointing at Merriam-Webster, which directly contradicts the entries you've drawn on in response.  Maybe British people think it means "especially in appearance?"  Maybe some Americans do.  Perhaps it's your intuition as well. But I don't.  Webster's doesn't. (see my first post for a full ref).

Or see any of the numerous quora refs above.  For instance, "the same/like-minded/share the same interests/dress the same/share the same interests and aspirations /have similar character traits or personalities .. or even may even look the same etc.".   Note how "or even in look the same" is an afterthought, the least important component.

I asked a random mid-50s American buddy of mine to describe what "two peas in a pod" implies, and he said "exactly alike".  And I said "exactly alike how?".  And then he proceeded to describe their personalities.

I know as a native speaker that many people simply do not think "peas in a pod" means "physically identical".  I barely consider "physical similarity" to have any link to the expression at all.  For me, this would strikingly jarring or misleading gloss in most cases that 瓜二つ would be encountered, which is an explicitly statement about physical appearance(perhaps like "peas" used to be). 瓜二つ seems to make no claims on personality, and "peas in a pod" definitely does.

I'd say the proof is in the pudding, as it were.  "peas in a pod" is not used by translators in practice. It's an extremely common English expression, so you'd think it should be a perfect match. (melons->peas). Yet it is quite rarely used(see reverso).  Why translate "瓜二つ" as "they're identical"?  Why not say "they're two peas in a pod".  Obviously *something* is not matching up.

So, maybe 60% of English speakers still think "peas in a pod" means "physically identical", and 40% think it means "very similar in mannerisms and personality".  I'm not saying anyone is "wrong" about the meaning of the expression. But why choose an idiom that's going to put off 40% of your readers?(or 20%, or 10%).   There are so many perfectly useful idiomatic translations that won't confuse anyone. Why hang on to this one? 

I saw the Collin's definition before posting.  Of course I searched for every definition I could find.  But I wasn't trying to trick anyone by omitting it, I just don't think it matters. It's only a good gloss if it's not going to cause widespread confusion among the translator's audience, and in modern English "peas in a pod" absolutely will.

Well, my 2p.

It's too bad about [expl]. I've run into these cases a few times now, and I honestly think jmdict would benefit from a policy change on this one. The etymology of idiomatic expressions can often be extremely helpful to learners for retaining the vocabulary. (and to translators, for a clearer sense of potential nuance).

@@ -21,2 +21 @@
-<gloss>exactly alike</gloss>
-<gloss>like two peas in a pod</gloss>
+<gloss>exactly alike (in appearance)</gloss>
@@ -24,0 +24 @@
+<gloss>(practically) identical</gloss>