I’ve seen it a lot in ‘90’s hacker / net adjacent cultures. It always reads as gen-x/elderly tech millennial to me - specifically post 1993 net culture but prior to mass adoption of autocorrect.

It was the norm on irc/icq/aim chats but also, later, as the house style for blogs like hackaday.

Now I read it as one would an hear an accent (such as a New England Maritime accent) that low-key signifies this person has been around the block.

Even more recently is a minor signifier that this text was less likely generated by llm.