I was using the shiny new "answer own question simultaneously" feature to write this post. I wanted the post to be CW, so I ticked the "community wiki" box, under the answer.
On saving, the entire post became CW. Now, that was my intention, but I expected only the answer to be CW (and then I'd have to use mod powers to CW-ify the post itself).
I tested it again (will be deleted soon), since I wasn't sure exactly what I'd done, the same thing happened. Looking at the revision history of the first one, one can confirm that the post was simultaneously made CW at the time of posting.
I, personally, don't think that this is by design. CW questions are discouraged/have strict rules, while answers are not. Wanting an answer to be CW does not mean that you want the question to be CW as well.
In fact, the mark-question-as-CW option has been removed (it's hidden away in the mod menu now), so I assume it's not something that's supposed to be really used.
Bug?
Update: Looks like this only happens to mods. I tried it out on Programmers.SE, and the question was not converted. Makes this rather trivial since it only applies to mods and we can remove CW-ness anyway.
[status-bydesign]
? CWness of an answer does not imply CWness of a question.