PS. I do fully agree with those who do not see the rank difference to judge the quality of a thread, not because I am one (lol), but because it is correct and the rightful thing to do.
Source? My time and my mind.
Maybe some users depend also on rank but it should be define that merits comes from any user and regardless of their rank.
The response by hilariousandco gives a good hint on how to define it. But you are right we have different perspective on how to view quality post/thread.
In my opinion, merited post with substantial information always depend on the taste of user some dont like it but others do so its not always the same. Especially when the one writing it is highly fluent into writing.