The convention on StackExchange is that signatures in Q & A aren't required, or desired:
We don't want to clutter up question pages with a lot of redundant signature blocks and taglines and so forth. While these are common on forums, questions and answers on Stack Exchange should contain only relevant content.
Please use your built in profile, avatar, and username as your signature; that's what they are there for, and every post you make is already "signed" this way!
I recently proposed an edit to an answer which corrected a spelling mistake and removed the posters signature. This was approved by one user and then rejected by the author of the answer with the (canned) reason:
This edit does not make the post even a little bit easier to read, easier to find, more accurate or more accessible. Changes are either completely superfluous or actively harm readability.
Putting aside the fact that it's a wildly inappropriate reason to select when rejecting the specific edits made, what is the convention/policy on coffee regarding having / removing signatures from Q&A? Is there one that differs from SE as a whole, or does the convention stand?