There is an issue open on ～もの/～もん entries, so there's no need to keep this edit open.

I agree it's a shame it makes the entry a little unsightly but I don't think the reading かいもん should be [hidden] away (but I wouldn't mind a tag like that applied to 買いもの；買いもん)

買い物	68063816	99.6%
買いもの	268422	        0.4%
買いもん	14236	        0.0%
---
考え物	71000
考えもん	9874    <- not in jmdict
比べ物	297511
比べもん	5424    <- not in jmdict
馬鹿者	91293
馬鹿もん	2534    <- not in jmdict
売り物	413791
売りもん	2456    <- not in jmdict

I can see the argument for keeping かいもん on this entry (as it's not really a separate word) but I don't like that it introduces unsightly restriction tags (if 買いもの and 買いもん are included as surface forms).
I think this is another illustration of how "hidden" readings/surface forms could be very useful. It would allow us to include -もん forms on other -物/-者 entries without adding any restr tags. I'd argue that even the reading doesn't need to be visible; what matters is that a -もん search takes you to the right entry.

OK, I'll put it back the way it was before the split. We can't have 買いもの/かいもん as a pair, and I'm not throwing away 買いもん.

@@ -16,0 +17,3 @@
+<k_ele>
+<keb>買いもん</keb>
+</k_ele>
@@ -18,0 +22,3 @@
+<re_restr>買い物</re_restr>
+<re_restr>買物</re_restr>
+<re_restr>買いもの</re_restr>
@@ -24,0 +31,3 @@
+<re_restr>買い物</re_restr>
+<re_restr>買物</re_restr>
+<re_restr>買いもん</re_restr>

https://www.1101.com/job_study/iwata/2008-04-17.html
安心して「バカもん！」と言える人と、
腫れ物に触るように
叱らないといけない人がいるんですよね。
(interview w Iwata, former CEO of Nintendo)

https://ja.wikipedia.org/wiki/人気もん!
『人気もん!』（にんきもん）は、2005年4月3日から2012年3月18日まで、テレビ新広島の制作により、FNS中国地方ブロックネットで放送されていたドキュメントバラエティ番組である。

https://dictionary.goo.ne.jp/word/似せ者/
daijs+ にせもん【似せ者】 の解説
松井今朝子の短編の時代小説。
(にせもん is also in our 偽物 entry)

https://ejje.weblio.jp/content/この家は売りもんではない。
tatoeba example: この家は売りもんではない。
This house is not for sale.

https://japan-indepth.jp/?p=64397
橋下氏も橋下氏で、ある学者の容姿を「安もんのヒトラー」などと形容したことがあるが、これは相手が先に自分をヒトラーに例えたことへの「言い返し」だと明言している。
(Hashimoto did write "yasumon" not "yasumono" on his twitter but you can find plenty of newspapers etc. using the kanji 安物 to quote him, i.e. https://www.tokyo-sports.co.jp/social/politics/468849/ )

I guess we haven't formulated an official rule on these, but the previous discussion was on this particular entry (and on a deleted 買いもん entry). かいもん is spoken language. it might seem rare in the ngrams because people don't write it out with much frequency, yet will still pronounce 買い物 as かいもん. It's super common in Kansai and probably all or most other western Japanese dialects as well (博多通りもん for example is one of FUkuoka's most famous omiyagegashi), and probably in parts of eastern Japan and even Hokkaido too. 物/者 can in many (if not all) commonly used constructions be pronounced もん. I think we should include it in more entries to demonstrate this. I don't think we should split them out because they are really just a different way to pronunciate the same word and as such they meet our 2/3 guideline.

@@ -21,0 +22,3 @@
+</r_ele>
+<r_ele>
+<reb>かいもん</reb>

買い物	68063816
買いもの	268422
かいもの	238334
買いもん	14236
かいもん	13489

I thought we were doing them on a case-by-case basis, and given the expressed interest in decluttering having two simpler entries didn't seem a bad move. I'd like to see the impact of similar handling of other 物 and 者 cases before attempting a general rule on ...もん forms.
Of course, we could just have かいもん as a [nokanji] reading, but that ignores that 買いもん seems to be slightly more common (and かいもん could also be referring to 海門 and 開門). With that many counts in the n-grams, I certainly wouldn't want 買いもん thrown away.

We've discussed this previously - I don't think -もん forms should be split off but kept with もの's, or each and every 物 and 者 entry could have a doppelganger もん entry (not that we include -もん readings in all of them, but we certainly could and probably should include them in more). I also think that we don't need to record the kanji surface form "買いもん" at all, and I don't think we actually need to include a note saying "かいもん is col". It's not as かいもの is a particularly formal word to begin with.

Yes. Done.

@@ -17,3 +16,0 @@
-<k_ele>
-<keb>買いもん</keb>
-</k_ele>
@@ -22,3 +18,0 @@
-<re_restr>買い物</re_restr>
-<re_restr>買物</re_restr>
-<re_restr>買いもの</re_restr>
@@ -28,6 +21,0 @@
-</r_ele>
-<r_ele>
-<reb>かいもん</reb>
-<re_restr>買い物</re_restr>
-<re_restr>買物</re_restr>
-<re_restr>買いもん</re_restr>
@@ -39 +26,0 @@
-<s_inf>かいもん is colloquial</s_inf>

Would it not be better to have a separate col-tagged かいもん entry? I'm not sure it's worth cluttering the entry just to accommodate a significantly less common reading.

mk

@@ -38 +38,2 @@
-<s_inf>買いもん is colloquial</s_inf>
+<pos>&vi;</pos>
+<s_inf>かいもん is colloquial</s_inf>

Not sure if かいもん applies to 買い物 and 買物, but it's definitely not 買いもの

@@ -30,0 +31,3 @@
+<re_restr>買い物</re_restr>
+<re_restr>買物</re_restr>
+<re_restr>買いもん</re_restr>

買い物	68063816
買物	4614770
買いもの	268422
買いもん	14236

It's so comparatively rare that I doubt it's worth mentioning.

"col." isn't the most obvious abbreviation.

@@ -35 +35 @@
-<s_inf>買いもん is col.</s_inf>
+<s_inf>買いもん is colloquial</s_inf>

買いもの	268422

@@ -14,0 +15,3 @@
+<keb>買いもの</keb>
+</k_ele>
+<k_ele>
@@ -20,0 +24 @@
+<re_restr>買いもの</re_restr>

NVm, should have actually checked the kokugos.

Except for slang/colloquial terms, I think 
we've decided (in the recent past) NOT to tag 
things that 1) aren't marked as vs in the 
kokugos, 2) are more commonly "-をする"

daijr, daijs, meikyo, gakken, smk
買い物に行く	234071
買い物をする	855570
買い物する	377651

@@ -29,0 +30 @@
+<pos>&vs;</pos>

I'll approve it for now. If anybosy objects, 
they can re-open it.

買いもん	14236
買い物	68063816
買物	4614770
かいもの	238334
かいもん	13489

OK, putting it back, and removing the draft 買いもん entry.

@@ -13,0 +14,3 @@
+<k_ele>
+<keb>買いもん</keb>
+</k_ele>
@@ -15,0 +19,2 @@
+<re_restr>買い物</re_restr>
+<re_restr>買物</re_restr>
@@ -19,0 +25,3 @@
+<r_ele>
+<reb>かいもん</reb>
+</r_ele>
@@ -21,0 +30 @@
+<s_inf>買いもん is col.</s_inf>

I agree かいもん probably shouldn't be here. I've proposed a split.

@@ -20,3 +19,0 @@
-<r_ele>
-<reb>かいもん</reb>
-</r_ele>

I'm not sure if including these sorts of dialectal readings is a good idea.
Wouldn't we have to be consistent with all -物 entries?

Since nobody has protested...
I think 買いもん is too rare to be worth 
recording (esp. as it'll be rather messy). I 
can see why it's unusual too as the IME isn't 
helpful at all when you type かいもん (開門、海
門、会モン、etc.)

@@ -19,0 +20,3 @@
+<r_ele>
+<reb>かいもん</reb>
+</r_ele>

鍋物	179878
なべもの	4030
鍋もん	1374
なべもん	567
買いもん	14236
買もん	78
買い物	68063816
買物	4614770
かいもの	238334
かいもん	13489

Scary prospect, but it seems that  買いもん, etc. are common enough to record somewhere.

https://detail.chiebukuro.yahoo.co.jp/qa/question_detail
/q144851974
"買い物←「かいもん」って言います？

私は『「かいもん」行って来るわ』って言うんだけど・・・。
みなさんはどちらですか？

「かいもん」って関西弁？？"
"地域、人によって「もの」が「もん」になまるのではないでしょう
か。
私は大阪人ですが「物」「者」はよく「もん」と言います。 例え
ば、
食べ物 たべもん
生もの なまもん
青物 あおもん
果物 くだもん
鍋物 なべもん
飲み物 のみもん
着る物 きるもん
履く物 はくもん
品物 しなもん
色物 いろもん
上物 じょうもん
安物 やすもん
本物 ほんもん
偽物 にせもん
瀬戸物 せともん
輸入物 ゆにゅうもん
翻訳物 ほんやくもん
書いた物 かいたもん
出来た物 できたもん

ほめる者 ほめるもん
笑う者 わらうもん
喜ぶ者 よろこぶもん
怒る者 おこるもん
泣く者 なくもん
悲しむ者 かなしむもん
よそ者 よそもん
筋者 すじもん
横着者 おうちゃくもん
極道者 ごくどうもん
馬鹿者 ばかもん"
"名古屋出身の者です。
”かいもん”って使ってましたよ．"
"「もの(mono)」が省略された、または転訛して「もん(mon)」にな
っているだけでしょう。
方言であるとは一概には言えないように思います。また、上品か下品
かなんて比べようとする(または、決めつけようとする)人って、心が
狭いと思いますが。

「物」だけでなく「者」も「もん」になります。
悪者→わるもん
・・・他にもいっぱいありそうですね。"
"大分寄り、山口寄り、の福岡県に住んでますが、
「かいもん」って言います。
多分、関西に限らず使ってる地域は結構あるのではないでしょう
か？"

Do we want to record this pronunciation? There's a whole 
lot of -者/-物 entries we could add -もん readings to if we 
wanted.
Also don't believe this is an adj-no.

@@ -22 +21,0 @@
-<pos>&adj-no;</pos>