I asked you "For $act=='upd' too?" and you said "Yes".
I thought - BOTH FOR ALL ACTS, the function is the same :)
You talk about the $userRegName variable, but I mean a password variable to define the allowed characters in a user's password. I didn't find one in 1.4.
Ah, got it. You've just said "Maybe there should a new variable like $userRegName for that in miniBB 1.5 setup_options.php" - and it already is something like this :) No, that option will not be included. Your problem is very rare, you are the first who is asking for this within a year. Most people are satisfied.
Personally, I think, there is no need to include something like these. People will include international symbols and they will be wandering later, why it is not working etc, etc... Why to have problems, if we are not having them? :)