If they update they will have problem since the irc servers treat lower and upper cases as different characters. The solution would be to tell all users that has a problem to deactivate utf-8 support in mIRC to be able to join their old channels.
I understand the problem quite well, and no, that is not the solution. The solution is to use UTF-8 channel names as suggested by Riamus. Again: want to know why the majority of users on those channels are on old versions of mIRC? Because those are one of the only clients that can visit these channels in the first place. In case you weren't paying attention, mIRC is one of the few clients that only recently started using UTF-8. Just about every other client already uses UTF-8 out of the box and can't even access your channel. So who are you really hurting? Users with old versions of mIRC-- nobody else.
