I did address your bug report too, I understand the point of your post is not 6.13, but we all get affected by other people not caring about their computers, so it's important to address that issue if it arises.
As I said "I've never experienced this issue with EFnet/Undernet/DALnet/IRCnet or any other network I've connected to. I can't see this being an issue with mIRC itself." - nobody else seems to have experienced this issue, making it less likely to be the mIRC program, and more likely to be a script or IRCd issue. We'll find out in the future I guess, lets hope future versions work okay for you

Regards,