Y'know, you're just capping a few words here and there, which I don't think many people find to be too annoying. It's illterate and execrable when somebody does whole sentences, which really does read like yelling instead of just emphasizing a word.

I'm all about the initial exclamation and question mark from Spanish, by the way, and I import it into English at every available opportunity. Unfortunately, I don't get enthused very often, so I don't normally get the chance. I can't wait for the day when it doesn't look weird to English speakers.

Finally, Strunk & White say that you shouldn't be using any of these emphasis tools: your writing should indicate the emphasis, and if it doesn't then you need to rewrite until it does. Maybe they're just stodgy.