I made a support request for this issue as well: 306585
In the past I'd get comments on my game with sketchy "download here" links, which I was able to report and delete. Now, I'm getting collections with only my game in them, and on the collection comment for the game is a sketchy "download here" link. When I viewed it, I found no way to report it. When I went to the user's profile, I was only able to block them and couldn't report them.
Can itch.io add an option to report public collections, and to report users? Or is there a way to do this already? Is anyone else seeing this type of spam on their games?