When a question gets 30 answers, it's automatically turned into a Community Wiki. That's not new and it's totally fine in my opinion.
Normally, it's supposed to show the following message in the revision history when the 30th answer is posted (for example, in this revision history - see Aug 11 '12 at 0:19):
Post Made Community Wiki by question having more than 30 answers
It used to name the user who posted the 30th answer, until this suggestion happened and it started showing the above message.
The bug: it recently did not work this way
A couple of days ago I noticed weird behavior in the revisions of the Top Bar announcement, where the 30th answer caused something like this to temporarily appear in the revisions:
Post Made Community Wiki by [name of a particular user]
The user was not a moderator and was not the question owner. It was in fact the user who posted the 30th answer - an ordinary, plain user. This was spotted and "fixed" manually:
Then, when the next answer arrived about 8 hours later, it re-triggered the Community Wiki conversion which shows up with the proper notice, as you can see.
Ordinarily, the only users who can convert a post into Community Wiki themselves are diamond moderators, as in this revision history. Nobody else should be able to convert a post into Community Wiki, except by posting the 30th answer, in which case they should not be named.
However, apparently, in this instance the 30th answer converted the post into Community Wiki and the user who made that post was named as having converted it into a CW post.
Was the bug fixed, or is it affecting only the first time question is turned into a CW?