Proffessional cartoonists use it because you don't get confusions like 1 l I (all three different things). In general caps are easy to distinguish from one another even if they're stylized. And going prosey only to internet shout...I'd suggest italics and an exclamation point, if it was /really/ over the top XD " . Internet shouting isn't quite impressive to readers. Excluding sound effects, bluh.