I started my response as follows:
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Every single JE I looked at (GG5, Eijiro, プログレッシブ, 等,) was quite unequivocal - it's cooking FOR oneself.
The 国語s are characteristically a bit vaguer, but I can't interpret Daijisen's "自分で食事をつくること" to mean anything else, especially as it follows it with "「 −生活」". GG5 glosses that as "a lifestyle in which one cooks one's own meals".
The Chiebukuro example is discussing a point a bit removed from the meaning of 自炊, and I can't really see that alone as grounds for a significant change to the gloss.
Do you really use 自炊 if you are putting on a dinner party? I suspect not.
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Then I glanced through all the examples in GG5 where it is used, and I found:
合宿中は当番制で自炊することになっている． During our training camp we have to cook our own meals on a roster system.
So the GG5 compiler(s) think it extends to cooking for others (presumably in a "self-catering" context.)
I'll add "self-catering", which is in many references.

@@ -23,0 +24 @@
+<gloss>self-catering</gloss>

I disagree Rene, the point of 自炊 is not necessarily that 
you're going to eat what you've cooked by yourself - you 
might be making something for a bunch of people. I should 
perhaps have clarified this but I thought the 知恵袋 quote 
was enough: "自炊のカレーで「おいしい」といったけど実はおいしくないといった経
験はありますか？". The meaning is obviously not "have you ever 
made a curry for yourself that wasn't tasty, yet you 
nevertheless said it was tasty?"

I think all bases are covered now.

shinmeikai
食事を賄ってくれる側の人が（たまたま）居なくて、自分で自分の食事を作ること。〔炊事に不慣れな学生や男性について言う語〕
meikyo
自分で自分の食事を作ること

?  no idea what was wrong with the original gloss, 'cooking for oneself'.  in fact, i'd say it's better than 'making food oneself', because 'making food oneself' doesn't necessitate that you're going to be the one who eats it (whereas that's the whole point of 自炊)

@@ -19,0 +20 @@
+<gloss>cooking for oneself</gloss>
@@ -20,0 +22 @@
+<gloss>doing one's own cooking</gloss>