User blog comment:MisterWoodhouse/Fandom is upgrading to a modern version of MediaWiki/@comment-675805-20190621023415/@comment-3582098-20190621065856

Capitalizing for emphasis derives from older grognards like myself who have been chat- and forum-goers since forever, before there were even the basic options to bold or italic text (and, frankly, in many that have come and gone, as well as stuck around, they still aren't available to users). It's not proper grammar for writing an essay, or writing an article, but for back-and-forth talking, it's still commonplace.