I'm sorry to say but I have to be doubtful after finding the pattern on itch as well, from a couple of different accounts that were both created shortly after the game page was published, having similar comments, and remaining inactive since. It is to a way lesser extent, but it being present here at all and it repeating on a wider scale way later on is too weird. Are these people you know? Is there anything you can do about the strange spam on Steam?
Also sorry but Michael Primo's reply reads a lot like one of those reviews halfway through, but clearly that account belongs to a real person so I don't know.
This is too weird and while I hate assuming the worst, seeing even a bit of it on itch way earlier than it happened on Steam is too suspicious to disregard.