It’s a bit selfish, but if I take the time to show up early and get a seat I am not going to make myself uncomfortable because you feel entitled. I’ll move a bit if there’s room, but if half the seating area further away is open then you can sit your late ass down there.
I think the towel thing is fine if it’s for no more than a few minutes. People do need to get up to use the bathroom or whatever. More than that? Hell nah.