Oh, there are several issues for the ratings system. For example: if you happen to have a module that some cargo cult follower does not like because the framework he/she uses dropped using it, you'll get a nonsense review with a single star rating. Or maybe the person is just an idiot and downvotes your module because does not like you. I'm glad to not have any of these idiots to rate my modules (yet!). However, if this is the case, then the other sane people will usually rate your module and with multiple stars :)

On the other hand, as people mentioned before, if you get a valid criticism you can try to fix the issue to resolve the reviewers concerns. I see that one of the reviewers deleted the review for example. As for the open source world, you need to wait for a response. I got a response from one of my bug reports in RT after 3 years for example :)