It's my experience that anything that whiffs of self promotion tends to get downvoted away, which seems reasonable.
Anything that expresses a non-mainstream opinion might hit the initial downvote limit, but recover over time if it turns out to have some merit. (My fascination with capability based security falls into this niche)
Something non-obvious, but informative, tends to get a bit of upvoting.
The rare really good point that builds discussions... those get rewarded richly.
So, the moderation system, as near as I can tell, works as intended. The feedback cycle takes a while to train us for better behavior, but it seems to work.
You do have to weigh all of the above, against the factors that overcome inertia, and lead to someone posting.
Most people reading are likely to see something expressed at least as good as they would, and thus just lurk.
It's only when you've got a nit to pick, or an interesting tangent, or need to self-promote, that people tend to post. These are the forces always pushing against moderation.