You however loose a big part of the feedback on individual posts When I get down voted I mostly think hard about why I was downvoted and make a effort to improve and perhaps even correct.

Upvotes seem less informative, they can mean "good argument","right argument" or even just "I loled at that".

This is a bit odd. The possibility of me improving seems to be higher when someone who knows what they are talking about says "do it like this" rather than "don't do it like that" (without following it up with a "do it like this").

This must be because posters infrequently down vote posts into the negative. They are far more liberal at up voting a post to 1, 2 or perhaps even 3 points (depends on how many eyes skim it).