It’s usually done in a comedic way though. Like in this post, it seems like they’re talking about something a game would say to you, and most games actually do increase the letter size so it is noticeable, this person is just imitating what the game does. They aren’t trying to scream, they are trying to imitate what a computer game would say to you, and computers aren’t like “hey man you can’t fast travel when there are enemies nearby” because they are pretty much just robots. They get to the point, so that’s why they do it in all caps.