I think the biggest flaws in the merit system has is ways that it's obvious to game the system... there are several things you can do imo that will lead to more merit opportunities that have very little to do with good posts, its just a way of manipulating attention in a certain light where it favors you.  Here are some examples, whether these are disingenuous or not I guess is up for debate:

1) Only posting in sections with high merit handouts.
2) Posting only on threads that are on page 1 (lol who doesn't do this besides signature spammers)
3) Berating others complaining about rules in order to appeal to more merit sources.
4) Posting threads as merit giveaways as a way of gathering merits for the topic creator.
5) Posts about merit achievements to farm merit.  (To be fair this one is less acceptable lately but in the beginning, some heavily abused this, and its just skanky.)

It creates an environment where there is less discussion and more just "talking at" the topic creator and trying to have the most clever response. It's less shitposting and spammy I guess but it's been replaced with 70 people in certain sections trying to rewrite the same answer to a question over and over in a way that's more clever than anyone else's which becomes just boring as hell to read as well.

To your point though, I'm not really sure that there is a big difference between high quality and something you agree with.. because high quality is subjective.. like what defines a quality post?  Something in English that answers the question first?  How about more elaborate?  What if its 10 paragraphs long?  I just don't see how you can unlink subjectivity from what is considered high quality, which is why my list above I feel exists.