Ask pg: What's up with the randomly [dead] comments?

Every day I see articulate, polite and relevant posts being flagged dead for no apparent reason. One of these posts was by jashkenas in a thread about CoffeeScript (http://news.ycombinator.com/item?id=2503653) I've added other examples below.

Is this a misbehaving bot or a rogue moderator with an happy trigger?

http://news.ycombinator.com/item?id=2582372

http://news.ycombinator.com/item?id=2566826

http://news.ycombinator.com/item?id=2566797