I understand what you mean. Whenever downvote occurs, it is natural for us to try to find out why, especially when there is no reason we can think of.
It happened to me several times when I got downvotes from a couple of people. I asked them the reason, they wouldn't even respond. Sometimes people say why.
It would be nice to get reasons. But if we don't get them, it should really matter either. Whatever the reasons are won't change who we are, and should really affect us emotionally.
I would just accept is as rewards disagreement, and leave it be.
Maybe not who we are. But if you tell someone his is spamming the shit out of the blockchain, he might reconsider if he/she got told :)
Some are don't care at all ofcouse :D
and yes, it can just be rewards disagreement :D