I know it has nothing to do with IDENT, but a secure connection is harder to crack.
EDIT:
https://www.grc.com/port_113.htm
I've just reread that, and it explains that IDENT was used to automatically identify users of FTP and such. The problem was the almost complete lack of security, so no-one trusted it. Even now, servers that do use IDENT don't really care whether the connection is accepted or rejected, and stealthing it has never caused me any problems.
Suffice to say, IDENT isn't causing any problems with MSN Messenger.