You can select a new file in Member Profile, so you can change your picture, but there is no way to edit the original posted text.
I think it would be good to have some editable information fields. Tech / Justine / MNers what do you think ?
If the board software makes this hard / impossible, maybe it could populate the thread with an 'About Me' type box whose contents are editable in the 'member profile' details. It could be made clear upon registering that this box could be left empty.
(Similar editing concept to friendsreuntied where you can repeatedly go in and edit your life story until you're happy with it).
(Well, happy with the editing, not necessarily with your life story)