So, as far as nominees are concerned, there's nothing prohibiting them from abusing with merit bribery, right? If someone wants to buy votes with merits, all that's needed is to merit them at some other post.
That's probably possible, or it can happen in a local (translated) topic. But it'll be hard to prove: I've Merited many of the users who have voted for me on other posts, but this had nothing to do with their votes.
The problem with this however, is that communication between the nominee and the voter is required (in contrast with previous contests wherein the voter knew it beforehand).
Or, without explicit communication, it can be implied. Or expected. There is no perfect solution, unfortunately.