So merits are just "likes" for useful posts. Am I right in thinking so?
Very much so. You only have to look to the volumes of merits the merit sources gift each other, or, to those they are trying to give a helping hand to rank up (instead of letting the system work as intended). Another one to look at are the merit sources who will dump seven or eight merits to nearly all users (because they can't find enough posts to merit) then dial back to just one merit to those they are in despute with.
...and it's not just "useful" posts that are showered with merits either.
Any suggestions on how to improve some of those dynamics that you have identified, timelord?
Maybe more merit sources, or rotate merit sources?
Or scrap the whole system?
Would you speculate that the merit system helped the forum at all since its January 2018 implementation, or did the merit system make the forum worse?