yes they do, but comments also appear to outside users! People who don't have an account here. So... I think comments are better?
What you describe does seem like mob mentality, which is common on the internet... but I'm not sure the review system is what's truly protecting developers here. Ill-intentioned people could still leave a negative rating AND a negative public comment... although that'd require 1 step more and thankfully people are lazy. I'd say one of the reasons there aren't many negative comments around is that... it's harder to get popular? maybe? idk, not an expert at all. I also very much like how friendly is itch.io to small creators and hope it stays this way.