I generally agree with you that reviews in general should be public. But while the way itch.io handles reviews is certainly unusual, to say the least, I didn’t feel like they made a big secret out of it. When you rate/review a game, right between rating and text there’s an info text that reads:
Your review
Share what you liked or disliked about this project. Our community rules apply here. Reviews are shared with developers and your followers.
So I think their kind words were actually meant primarily for you. :) Awww…
If this ever got changed, it would have to be an opt-in kind of change. I feel like people would riot if they signed their for your eyes only review with their real name, their email address, or included other private information that they didn’t want to go public. (Right now there’s an option under Privacy that enables users to hide their reviews from their followers.)