I tend to be more forgiving with "thread drift" in a forum. Probably because I got into this forum thing later in life.
Things like typing in all caps, drift, and debating don't bother me one bit. It's the usual mix of things that might happen if we were all together in real life at dinner.
However, things like poor syntax and spelling, bizarre abbreviations, too much reliance on smilies, pages without paragraphs and continuous cutting and pasting drive me around the bend.
In chat, I can ignore the chatterboxes by perusing over them, much like "tuning out" a guy over drinks.
However, if someone I know and like enters, I can engage them.
I just wish I had a cyber-kinetic-smilie pool cue to smack the drunks, like in the old all-real days.