Yeah, goodness is a personal conception, whatever - perhaps there is no way to determine whether a post is absolutely good. Whether the posts are objectively good is entirely unimportant, though - goodness is defined by either the decision-makers' opinion or the majority's opinion. It's simple, now, come on.
I think I've found a good baseline of quality, somewhere to place a 0 on the Insult scale of goodness - look at this poster, Centaur. Whorely thoughts? Insane ideas? As long as you write something, anything, more intelligent/interesting than that, and continue to do so, you will probably be fine.