Programming lets you do anything in terms of detecting something you want to ban.
It's matter of how annoying it is, and how much you're willing to pay to stop it.
Career programmers cost money, and ideally they do nothing but e.g. develop apps and games like puzzle rush that make you money. It's far less than ideal to have them working on stopping spammers all the time.
In particular if the spammers aren't bots... if the spammers are just kids who post something over and over, it's really not worth spending 5 figures on. In other words over $10,000
Chess.com has all these bots auto-banning and auto-muting people , for half the time, dumb reasons. But Chess.com just can’t make a simple bot to detect spam in top games chat. It’s kind of ridiculous. Just make a bot that detects when someone post the same thing several times and mute them. It’s childly easy, yet chess.com doesn’t do it and makes people sit there while an annoying person post