Someone edited my question, moving the question mark outside the quotation marks. This is not correct usage in the U.S., as it is in International English. Which convention does english.stackexchange.com itself follow, when an issue like this arises?
Jimi's edit is correct. In American English, periods and commas always go inside quote marks, while question marks follow logic. In British English, they all follow logic.
@jasper clarifies your particular case. But answering the title of this question more broadly: I think the general policy has been that either is acceptable — each contributor writes in their own variety of English, and one shouldn’t “correct” someone else’s post just to change it from one reasonably standard variety of English to another.
I would definitely avoid making "corrections" that are really just editorializing in disguise.
I think an error is only truly an error if it's wrong in both British and American English.
Some of this will depend, perforce, on the skill of the editor. If you are fluent in British, American, and Canadian usage, then you can easily recognize a national convention and of course you'd leave it alone.
If you lack such an ability, then you should be extremely cautious in editing the work of others in an international forum like this one. Also, the differences in usage among these three nations (Australian is approximate to British standard) are not extensive and not difficult to master.
Personally, if someone were to move my "comma inside the quote marks" to accord with a different convention, I'd be utterly furious.