The rules you are referring to apply to news and email. They were not designed to apply to URLs in all context. The reason they are for news and email is because of hard line wrapping. Many email clients insert a \r\n after a certain column length, this would cause a URL to be split over multiple lines. IRC doesn't have this problem. Neither mIRC nor any other client I've used has any problems with understanding a URL split over two lines, so having <> around it wouldn't be of any help. And if it really annoys you, mIRC allows you to customize the hotlinks to your liking.
/help on hotlink
