There seem to be accounts that automatically downvote against an upvote that some of the most powerful accounts make (eg. xocd, xappreciator...), but these automatic downvote accounts are small and not powerful and have no effect...

I had a quick look at your account... you have posted about 10 times and haven't received downvotes as far as I can see? I think you've had one post muted - I presume for not being in the appropriate community?

Has downvoting been a real problem for you? Or just other people you know?