itch.io really needs to come up with ANYTHING for us to deal with this spam. Since we have plenty of power on our own stuff's pages, I feel like having a checkbox that says "Allow HTML in comments?" would be a good start - that'd deal with links and images. Deimus' idea of having comments in a moderation line, where they won't appear to anyone else is also a good option, I think it would fit perfectly with the HTML checkbox - if a comment has any <tags>, it goes to the moderation line and awaits for approval.
What is catching my attention now is that some of the spam is linking to itch "games", which I bet are just a bunch of malicious javascript code.