I concur, after the forum software update my forum name has been "cut" to lorenzo_michele and so far it seems there is no way to revert it to the original "lorenzo_micheletto" or at least change it to a better nickname.
I really would appreciate the ability to change the user name. I understand that it takes time for all of us to use this new forum, but the previous one has been so much better imho. So any improvements of this new forum would be great.
Strongly seconding/thirding this notion. I have no idea how my name got stuck in its current state, but for now I keep hunting the 'change username' button...