Why do people speak like this in their youtube comments?

Hey, i’m just curious and wanted to ask, but why do certains people in the comments act like this? I don’t really want to call out any channels but I’ve noticed that on most british youtubers, for ex. Pointless, Joe Sugg, Dan Howell, etc. there is always a bunch of people in the comments that speak like this. What is the deal with this?