If you look at the recent activity on openreview you can see that reviewers can still edit their reviews and change their scores. I don’t think anyone can post completely new anonymous replies though.

Same. I also did many additional experiments, but complete silence from the reviewers. It really sucks and makes me feel a bit helpless. I’m used to reviewer roulette in general, but it feels even worse in this case because I see other submissions where all 4 reviewers are engaged and raised their score after the author response.

I would kind of understand disinterest by reviewers if my submission had very bad scores and would be hopeless anyway, but I got 8855 and was very positive that I could at least increase one of the 5s to a 6 with my response.