Thanks (and upvoted) for listening. We cap downvotes based on karma because we've historically had problems with downvote abuse and we don't want it to be trivial to spin up your own homegrown downvote brigade; we don't similarly cap upvotes because that hasn't historically been as much of an issue.

That said, paying people on Mechanical Turk to upvote your comments is definitely bad behavior, although to my knowledge we don't have any set policy for dealing with it. I'd recommend starting by confronting the user, which you may have already done. If that doesn't work, I'd say you should take your evidence via private message to an active moderator; user Viliam_Bur is probably your best bet. If that doesn't work, only then would I take the issue to the userbase at large, e.g. by starting a new Discussion thread (which you don't have the karma for right now, but getting the karma would probably take no more than an introduction post and a couple more productive comments).

Discussion threads, once you get to that point, are created by clicking the "Create new article" button near your user information, in the upper right of the interface. There's a dropdown menu in the next screen where you can select where to post to, and Discussion is one of the options.

Moderator here. This is definitely not the way we communicate here. Accusations should come with some evidence. Since there is nothing positive written using your account, I am going to ban it now. If you are still interested in a discussion (by which I mean discussion, not downvoting), you can have a fresh start with a new account.