Honest question though, when is it ever appropriate to yell? Have you seen people ever do it? I think the all caps could be a useful tool for emphasis. Would I do it though? No.
> Please don't use uppercase for emphasis. If you want to emphasize a word or phrase, put *asterisks* around it and it will get italicized.
https://news.ycombinator.com/newsguidelines.html
Of course, uppercase is appropriate for an acronym or initialism that actually is spelled that way, such as SEO in the comment we're replying to.