In the past few hours, my total karma score has dropped by fifteen points. It looks like someone is going back through my old comments and downvoting them. A quick sample suggests that they've hit everything I've posted since some time in August, regardless of topic.

Is this happening to anyone else?

Anyone with appropriate access care to investigate?

To whoever's doing this — Here's the signal that your action sends to me: "Someone, about whom all you know is that they have an LW account that they use to abuse the voting system, doesn't like you." This is probably not what you mean to convey, but it's what comes across.