What's going on here?

One thing you didn't mention - probably because you don't know that - is that your comments in the discussion thread you linked run contrary to a position that's very firmly established on LW: that it's only rational to donate to one charity, the one you judged to offer the maximum utility. For example, this post makes this point very forcefully, but it also runs through several of Eliezer's posts in the sequences. Your arguments in the linked thread can be seen as annoying rehashing of arguments amply covered and refuted in those posts, and that could cause people to downvote you in greater numbers than you would guess based on the comments' content.

However. Having said that, the loss in karma is very heavy, and seems to affect comments of yours that have nothing to do with that thread, and don't really deserve negative karma. Assuming your numbers are correct, I see three possibilities:

1. You're being karmassasinated by random LW users irked by your comments in the linked thread.
2. You're being karmassasinated by a group of LW users working in concert for whatever reason ("hey guys, he sucks - let's all go and downvote his recent comments")
3. You're being karmassasinated by a sockpuppet network.

I find myself thinking that 3 is the most likely explanation given the evidence (that surprises me). However, I don't rate it much higher than 1.

I don't really have much to add, but since I mildly expect this to be downvoted, I'd like to add as a data point that a) I don't mind this post though I would not like such posts to be commonplace, b) the downvotes seem suspicious to me too, c) I do not think they were fair and d) I would personally be a bit upset if this happened to me and wouldn't want to be further punished for having brought it up.

My prior, given over 100 karma lost in an hour, obviously, was karmassassination. But it would be difficult for a karmassassin to give large amounts of negative karma to a relatively few number of posts, however, given the restrictions on new accounts to downvote. (I don't think you can downvote until you have positive karma?)

Hmm... could be somebody's been actively maintaining multiple accounts to keep this option open; or there could be an organised brigade of downvoters who have really taken umbrage. Both seem unlikely, but not as unlikely as many people individually deciding at the same time to downvote many of your posts. A puzzler.

1.  this is first
2.  this is second

As a reference, user: sam0345 rarely receives downvotes of the quantity which user: RobertLumley has received. This is rather aberrant.

Yeah, looks like sockpuppetry.

I've been on this site for several years, and I still don't know who is in charge at the deepest level (technical administration, let's say), so I don't even know who you can appeal to for help, whether IP addresses for downvotes etc are logged, and so on.

Robert, has any moderator or system administrator contacted you about this and said they'll look into it? Or is this episode just going to sit there unexplained and unaddressed?

Karmassassination is my best guess. Most of your posts seemed not to be bad, and in a couple of cases they seemed insightful.

This comment's karma really surprises me though, not because of the post quality, but because 41 people looked at and downvoted it.

"but I am considering leaving LW over this"

Is the utility of LW to you so small that a mere change in your karma number makes the consideration of departure reasonable?

For what it's worth, I recently took what I considered an unreasonable karma hit on a particular point I made. It was the most karma I ever lost on a single post, and I'm quite sure I've been a bigger jerk in the past. So my estimate is that more people are exercising their right to ding karma these days.

Hmm regarding the donations to multiple charities - sorry for offtopic but I just want to post something vaguely in agreement.

I see that if the function which determines which charity is the best, may be exploitable, donating to top 5 charities or so which are substantially different (not cloning each other) would reduce the pay-off for finding an exploit in this function.

I think of it this way. If i were to make a charitable bot, would it be most effective for this bot to donate to just 1 charity that it determines based on some function? Big red bold NO because this bot will be deliberately gamed (on top of failing consistently) It's why we need Google to return >1 search result. The first result may not work for the user at all.

Adding jitter/dithering to inexact calculations to improve resulting behaviour is common practice. If you have a target-shooting AI in a game, when it's shooting at it's best prediction of the target position, it is easy to evade. If it jitters some, it may score far more hits.

edit: Matter of fact I did write a shooting AI that did just this, and it made the AI more effective. If said AI was sentient but not clever enough to understand my rationale, this AI would either justify it with faulty logic or try to get rid of the fuzziness and jitter i've added (and then this AI would ponder why it is not becoming more effective).

Humans of course would, too, implement this sort of jitter and added fuzziness to their decisionmaking they'd pick from others when growing up, usually without understanding of the rationale behind it; backing the heuristics with faulty logic or dismissing it based on the faultiness of the logic.

On the topic of Karma, I can't be the only one here from the old Extropian mailing list, where, if I remember right, we had rather extensive collaborative filtering and voting schemes built into the mailing list software in the mid 90s.

It's pitiful that more than a decade after PageRank, the Web 2.0 has "advanced" to an additive thumbs up/thumbs down model on user forums. At this rate, we'll catch up to Usenet functionality in 50 years, and PageRank in a 1000 years. So much for the law of accelerating returns.

Please alllow voting to only those people who've accumulated +100 karma already, and even to them allow only 10 votes per week.

Unacceptable. I will take care of this.