I was in a channel with 900+ users and I was thinking about the IRC protocol and wondered what would happen if I typed "VERSION" in tha channel. Sure enough.. I was flodded with CTCP replies. Weird huh?
How is this a bug? Just about every client responds to channel CTCPs, including mIRC, xchat and irssi. mIRC can't control what other people send you, if you don't want the version replies don't send a CTCP VERSION.
That isn't a bug, a CTCP is just a normal privmsg, so if you send the exact same privmsg that typing /ctcp #channel version does then the other clients won't know the difference (because there is none) and will reply to you.