If everything or nearly everything in a sentence, post, or article is in all caps I take it as yelling. Or someone being plain obnoxious if it is a long post. I use all caps for a word or two at times for emphasis if I can't bold something, but that's it. I won't read lengthy posts from someone stuck in caps lock mode, it is hard to read and honestly it annoys me almost as much as "chat speak."

If it was entire sentences, I'd call it yelling. But just a word or two is fine for emphasis or excitement.

Yes but not necessarily bad shouting. Sometimes I just interpret it as, I dunno, typing loudly and with enthusiasm.