A fair question. As the "finger" hovers over words in the window, mIRC scans through the nicknames/notify/etc. list to try to find matches for that word. If it finds that the word is a nickname, its a match. If the word is surrounded by non-alphanumeric characters, mIRC strips the first set away to see if it can find a nickname match. It's not a foolproof method but seems to work for most situations
