Yeah, this happens to my account. I think I must have made some off-hand comment once that someone did not like and it's their petty vengeance. The DVers will wait about 2 hours (+/- 1hour, random interval) to do so, no more after that normal distribution. The comments are stupid stuff too, like some links to wikipedia pages and just random comments. The ANOVA I did on the DVs showed just random timing and comments (p-val was super high though, as I don't have many comments). It's strange.
Only way I can think to fix it is to tell people to stop talking about HN. If you want to keep HN good, keep it to your very close friends and family. We don't want this to turn into reddit or digg.