The quality of a post is often a subjective thing, because not all people have the same criteria, and I think that is completely normal.
That's it!It's the same way I've maintained that meriting a post is also a subjective thing. Each individual merits what they thing makes sense to them (I ain't going off track with this), and what makes sense to them may not make to others. It's that simple. Back to quality posts: I like reading well punctuated and concisely written posts. I have to understand a writer's point of view first hand (and almost immediately while going through not) before I deem it quality enough.