You can only edit a message you wrote for a few days. After that it is locked. (I suspect this is meant to be an anti spammer feature, so if your account gets hacked the hacker can't change all your posts)
You could ask an admin to change it after that, but it better be very important.
Edited 1 time(s). Last edit at 11/03/2018 09:51PM by Dust.
