I understand the rational behind not allowing users to
edit their own comments, but I have an alternate idea:
Why not allow users to append text to their posts? The
appended text would carry an additional timestamp so
that readers would know when it was added and could
determine which replies were written before or after it.
This would allow people to correct mistakes in their
posts in such a way that others are likely to read the
corrections. I know sometimes I have posted
information that turned out to be outdated or just
plain wrong (oops) and wished I could more easily alter
my post to say so, both in order to prevent moderators
from modding up my incorrect information and in order
to stop the inevitable stream of people flaming me for
being wrong. Unfortunately, simply posting a reply to
my own post doesn't seem to do the trick, as most
people don't bother reading replies.
On a related note, perhaps it should be possible to
cancel positive moderation on your own posts, incase
you find out that you are wrong and don't want to
spread incorrect information.