Lack of comments makes me think it all works correctly.
Based on observation, I'd think that's generally reasonable (though I guess not absolutely, based on post 8).
To have poor ratings but no comments appears like something is wrong.
Here I think you might be over-thinking things.
I suppose you could put some variation of this in an uploads opening comments, worded carefully so you're not fishing for insults:
if you rate my work [deleted], please tell me why in the comments. I just want to be sure that things are working correctly. I will gladly try to fix any issue if I'm made aware that there is one.