It looks like I can only edit my own messages. I think this is really unfortunate, because on a wiki, there are plenty of valid reasons to edit other people messages. For instance:
- a message contains something that breaks the layout of the page (a template with a syntax error, a gigantic picture).
- a message contains a broken link to an article or a discussion.
- new users often post messages without realizing that what they write will stay public for ever, and give e-mail adresses, personal phone numbers, etc. I usually remove those, although I don't want to hide the whole message in such cases.
- less common case: replace every occurrence of the real name of a user on the wiki, after a user rename request.