The effect appears to be small. I don't know if the database logs times of votes, but the times of actual posting are fairly homogeneous, so being a top post early on isn't a big enough advantage to stay a top post forever.

I did notice an interesting trend for the number of upvotes to as a function of place to undulate in an unexpected way, indicating either that people are upvoting slightly differently based on quirks of the number or based on page position in the "top" pages.

Only the top couple of posts appear to be abnormal in number of votes accrued. The kinds of echo chambers I was worried about would have had everything on the first page upvoted and few bothering to go the second page - there might be some upvoting of Generalising from One Example going on, but that would happen simply because it's the best post so far and not because the community thinks it's good.

Also, seeing Humans are not automatically strategic make it into the top-voted recently is good evidence against an echo-chamber.

As for the anti-kibitzer? The only thing I noticed was that snark and sarcasm are interpreted as positive or negative depending on the poster's reputation. Someone like wedrifid or Eliezer_Yudkowsky scores generally positive karma for such comments; most other score neutral or negative. This doesn't bother me, as I am well aware of how difficult it is to communicate such forms of humour - and a major part is having enough goodwill for the name attached to the post to even consider snarkiness or sarcasm. Only certain people have enough reputation around here to pull it off. Overall, I think that's a good thing: snark and sarcasm are great fun, but distracting and detrimental. When applied to an undesirable topic, the distracting and detrimental parts are also good things - but LW has lots of stuff I really want to discuss and see discussed, so the current low level of sarcasm is great.