we are talking mIRC here, not other clients or telnet connections. It is very easy for mIRC to append such value beyond your control when it sends USER data.
Say your fullname reads "D3m0n rox" and say assigned ident would be some value T74B7F503
mIRC would send USER data would look like this:
USER T74B7F503 "yourisp.net" "irc.some.org"
3m0n rox T74B7F503
If there was an ident request later on the same value of T74B7F503 would be sent by mIRC.
This is not aimed at you in particular, but how about the next reply in this threat concentrates on ideas on how to improve the security and not on "this would not work".
It can all stay as it is, and there will be more drones, more floods, more abuse.
It can all stay as it is, and "educated" reccomendations on this very forum will be for users to disable firewalls cos they don't know how to configure it for ident replies.
It can all stay as it is, there is nothing that can be done.