I hate that and people who share their links in chats where it says not to. I've been combating this the same way you have, talk to them, if they do it again, send a downvote. I absolutely hate it. I remember when I was approached by so many people at once, i tried helping them at first, but soon realized that it wasn't going to work. If you go on discord now, I'm rarely ever online(but I am, just show myself as invisible) and thats to stop people from sending tons of dms with spam.