First of all, there is normally no point to reviving old threads on the forum. This thread had been dormant for seven months and just woke up through your post from hibernation, only to find that the context has changed quite a bit and, as a result, may end up being counterproductive.

The list you mention may include some, but certainly not all not. Neither are all users on that list a Merit Source. What’s more, the 36 newly added Merit Sources have just started-off, so any try to detect them will result rather futile for the time being.

The quality of a post is complete subjective, so the more Merit Sources and forum members in general that award merit, the more diverse criteria there will be in that definition (which is an advantage to all). There is not standard de-facto.
I personally favour more those posts that debate and express a well-versed opinion to some degree of extent, but many other sorts may qualify such as informative, witty, controversial, that expresses my opinion better than I would do, that makes me think that I may be wrong, and so on.  But that’s just me.
I also tend to look at the posting history, needed to get a rough general idea of how a poster posts, and to detect posts that may attract my attention but do not blend in with history – these are usually plagiarized and a waste of time for all since the more we need to investigate a post, the less time to be reading and meriting others.