I looked at the posts in the OP and I noticed two things:
1 - You cited many posts from Review Master. If you do become a merit source, I would encourage you to spend your merit to a diverse group of people, while still spending near your maximum amount of merit.
Nice observation and I observed same. But I think there is no problem with that, I said this because I have read where theymos said something about this. I will not quote him because I may not provide exactly his lines but he is of the opinion that it is better to dump 50merits on one quality post than to split the merits to non quality posts for the purpose of fairness or circulation of merits.
Therefore, it could be possible that Review Master made majority of quality posts in the board as merit is supposed to be giving based on post quality not on individuals .