That was advice to developers that have the custom css feature enabled.
It would simply hide all the comments that have a link in it. No matter what type of link.
There was a huge spam wave a while back. Look at the age of the thread. You could go to certain games any time of the day and find scam comments with links, promising updates and whatnot. Developers have to sleep too, and could not keep up deleting those comments.
What you see nowadays is users complaining that they cannot comment at all, because Itch installed a very aggressive spam filter.