is there any actual evidence that the system works for the purpose that was created at this point? 
Yes, the number of spammers complaining they'll never be able to rank.
So i assume the answer sadly is no.
For that beside there was no need to come up with a bad idea poorly executed. Was just enough to freeze the ranks.
Youre mistaken sir, merit system is working as it supposed to be, because it helps people be more concise in what their posting about. And it also dramatically reduce shitposters as well as account farmers because they wont get anything with half assed post.
Lastly their are some cases alt accounts being detected because they can track the merit given massively to unworthy post.
Surely all the new system does is create an external marketplace for selling "Merit" (i.e. Fiverr etc)?
Dont need to create anymore section. Even though theymos stated that merit selling is not that big issue, it is still unethical to buy merit to others. Merits must be earned not bought.
Edit: fixed typos