"Rep grinds" (see how MMO-speak has influenced us?) on non-gaming web sites may be becoming the norm. You grind out some rep, and get privileges based on that rep. One can argue that this serves as an effective barrier to keep out would-be posters of bad content and discussion, but as we can see it also screws with "legit" posters. Determined individuals will figure out how to work the game to their advantage, both for good and bad.
What game and what advantage? It's a Q/A site. The only way you are going to game the system is if you ask clearly delineated questions and provide thoughtful and clear answers.
Form a cabal of vote sharers, who always vote for each other's posts. Post a bunch of semi-plausible content once a day and you'll have tons of karma in no time.
Post quick responses that have little insight. You'll always get votes for being first.
Post LOTS of trivial questions. More people will upvote than will downvote on the whole.
All the things you mentioned requires a lot of effort. In fact it's more effort than just actually providing one or two good answers and questions a day. Also, I have never seen any of the popular answers get answers that are not really close to the mark. Even the unpopular ones always get good answers that float to the top. Organizing a cabal of voters and then monitoring new questions within your area of expertise just so you can post semi-plausible answers to move up the ranks is borderline psychotic and I have yet to encounter these people on SO.
