But past a certain point -- somewhere in the 200-500 range -- more karma just doesn't matter very much when assessing a user account.

Huh? If karma isn't very meaningful past a certain count, why keep track of it at all? Why not just call everybody who reached 500 karma points "vetted" and leave it at that? (I suspect the answer is that karma does matter to some significant portion of the people here, but I'm open to hearing why you think otherwise.)

The "who we like" part seems to be how some people operate, especially vis-a-vis mass downvoting. I view that as counterproductive. What the phrase "furthers our preferential ends" denotes is not clear to me

"Who we like" could include mass downvoting. More than it, it involves applause lights hanging above certain members who espouse popular views or who have done something, apart from making a rational comment, to garner favor in the group. This could be proofreading a LW-approved text, organizing a meetup, etc., etc.

The key characteristic of this earned karma is that is has zero to do making a direct contribution to a more accurate map.

It's is just interesting to me because it's a lot like the church from whence I came. Signaling devotion to the cause becomes more important than being right about the merits of the cause.

LW is a community specifically committed to the mission of "refining rationality" and, therefore, (you'd think) making sure things like karma systems work to incentivize members toward that end. I don't see that happening.

LW is the best blog/forum I've seen -- virtually troll free, consistent flow of interesting articles, thoughtful & well-written comments, lots of people waaaay smarter than me, etc. That is part of why it is so interesting that the karma system seems so...weak.