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.
You are using the wrong standard. I believe it is best to award merit to posts that a lot of effort was likely put into making. It is possible a one liner is deserving to have merit, and it is possible a 10 paragraph post should not receive merit if it is incoherent. The basis for giving merit is if a lot of effort was put into creating a post.
The ultimate goal of merit is to eradicate people who post as many posts they can quickly in order to "earn" as much money they can via signature advertising, which market forces have caused to pay by the post. If people who put a lot of effort into their posts are rewarded by being allowed to rank up, those who create a lot of low effort posts will leave when they can't rank up.
In general, if a post is funny or witty, chances are, not a lot of effort was put into making said post. Most of the time when I say something funny, it is because I reacted to something I read or heard, and thought of something funny off the top of my head. I wont necessarily spend a lot of time trying to find a way to make something funny.
My concern is that many of the posts cited in the OP were low effort posts, and as such, I don't think deserved merit. I think it is pretty clear those posts (and many more throughout the forum) received merit because the merit sender agreed with the content of the post. The problem with this kind of behavior is that it will encourage the forum to become an echo chamber, and will encourage others to agree with those who clearly have merit to spend.
The underlying root problem with the merit system is that merit is valuable based on the fact that merit ultimately allows someone to earn more money via signature campaigns by way of having more signature features, however merit cannot be easily purchased with money. There are however implicit barter transactions for merit when people back someone with sMerit in a dispute. It would be more appropriate to allow people to buy merit so they can have more signature features, and so they would have incentives to not go around posting a bunch of nonsense and garbage because if they did they would lose what they paid when they get banned.