Its not possible afaik. You could ask one of the devs (nemo, sheepluva, koda, FireFox, unC0Rr and Tiyuri(Uriah) (I have probably forgoten someone(s))) if they can do it.

Combz is a self-proclaimed master hacker whom is certainly able to do this for you, if you're unable to contact any of the developers.

Keep in mind alex your forum and game accounts are linked.
Why are you wanting to do this? You want to change your name?

We could do that for you too, without a deletion.

hi, want to change my name tooo
to Juest

Hi guys... i have a problem to connect with my "two years used" nickname ,,Falkenauge"... the only way i can enter is to write it with an f insted of F >>(falkenauge) but i dont like that so mutch can you help me out?

Thank you

My guess is you were already signed in with the upper-case name somewhere else?

Either that or you recently changed the password for Falkenauge on the web server and the game server hasn't picked it up yet.
In that case, wait an hour or two or ask an admin to clear the account cache on the game server, or keep using the old password on the game server in the interim.

i like hedgewars