Many thanks for looking into this!
What have you/they been trying to do? Unsupervised detection of mass-downvoting, or exploration of particular specific cases alleged to have occurred? If the latter, do the records not show the downvotes at all, or do they show downvotes from many different individuals in each case?
(Does the database contain information about when any given downvote happened? I guess probably not, which makes diagnosis more difficult.)
For example: I've been having ~5-10 recent and older comments downvoted per day, I think all during UK night-time or early morning (i.e., roughly 4pm to 2am Pacific), most days (I think all) for about the last 4 or 5. Approximately all of the recent-ish comments I've checked appear to have been downvoted exactly once. (A few very recent ones haven't been. A couple have been downvoted more than once; I guess that they were genuinely disliked on their (de)merits.)
If someone has the time to look, it would be interesting to know: Do the records show that those comments have been downvoted, and by whom? One downvoter, or a few, or many? Any signs of sockpuppetry, if many?
One possibility (though an unappealing one, not a very likely one a priori, and one that I feel a bit paranoid even mentioning) is a sort of downvoting ring of people willing to cooperate on downvoting at a rate just slow enough to avoid suspicion. That would be bad. And also sad.
[EDITED to add: I'd offer to help with the investigating, but as an interested party I probably shouldn't.]
[EDITED again to add: at 2014-02-15 08:41 GMT, it looks as if I haven't had a pile of downvotes in the last 8-10 hours. Maybe whoever it is has got bored, or maybe they've noticed evidence of someone looking. Or, of course, maybe I'm making the whole thing up, but anyone who finds that likely and cares to check can look at my comment history and see the evidence.]
This is exactly the pattern for my downvoting too.
To whoever has for the last several days been downvoting ~10 of my old comments per day:
It is possible that your intention is to discourage me from commenting on Less Wrong.
The actual effect is the reverse. My comments still end up positive on average, and I am therefore motivated to post more of them in order to compensate for the steady karma drain you are causing.
If you are mass-downvoting other people, the effect on some of them is probably the same.
To the LW admins, if any are reading:
Look, can we really not do anything about this behaviour? It's childish and stupid, and it makes the karma system less useful (e.g., for comment-sorting), and it gives bad actors a disproportionate influence on Less Wrong. It seems like there are lots of obvious things that would go some way towards helping, many of which have been discussed in past threads about this.
Failing that, can we at least agree that it's bad behaviour and that it would be good in principle to stop it or make it more visible and/or inconvenient?
Failing that, can we at least have an official statement from an LW administrator that mass-downvoting is not considered an undesirable behaviour here? I really hope this isn't the opinion of the LW admins, but as the topic has been discussed from time to time with never any admin response I've been thinking it increasingly likely that it is. If so, let's at least be honest about it.
To anyone else reading this:
If you should happen to notice that a sizeable fraction of my comments are at -1, this is probably why. (Though of course I may just have posted a bunch of silly things. I expect it happens from time to time.)
My apologies for cluttering up Discussion with this. (But not very many apologies; this sort of mass-downvoting seems to me to be one of the more toxic phenomena on Less Wrong, and I retain some small hope that eventually something may be done about it.)