There is no limit is the number of votes they can receive, but there is a limit on how many points a user can get per post.
The current limits are +200 and -40. So if a post receives 20 upvotes, the user will get 200 points, but any upvotes after that they won't get any points. And if it got 4 downvotes, they would lose 40 points, but more downvotes won't lose them any more points.
