From this 2001 article:
Eric Horvitz... feels bad about [Microsoft Office's Clippy]... many people regard the paperclip as annoyingly over-enthusiastic, since it appears without warning and gets in the way.
To be fair, that is not Dr Horvitz's fault. Originally, he programmed the paperclip to use Bayesian decision-making techniques both to determine when to pop up, and to decide what advice to offer...
The paperclip's problem is that the algorithm... that determined when it should appear was deemed too cautious. To make the feature more prominent, a cruder non-Bayesian algorithm was substituted in the final product, so the paperclip would pop up more often.
Ever since, Dr Horvitz has wondered whether he should have fought harder to keep the original algorithm.
I, at least, found this amusing.
I'm not saying that your proposed algorithm is wrong - not exactly, anyway. I am pointing out something that I think is a flaw.
Putting the same point a different way:
Consider two comments. One is posted early, and is seen by 50 people. It's slightly good - good enough that each of those people would, by your algorithm, upvote it, but no better than that. The other is posted late, and is only seen by 10 people, but it's very, very good. According to your algorithm, the first one would get a score of +50 and the second one would get a score of +10. By the methods currently in use, the first one will get a low score - probably +1 or +2 - and the second one will still get +10.
The first comment got many more points than the second, by your algorithm, because its author was able to quickly put together something good enough to be upvoteable, and because they were at the right place at the right time to post it early in the conversation, which implies either luck or lots of time spent lurking on LW. I don't think these are things we want to incentivise - at least not more than we want to incentivise putting time into crafting well-thought-out comments.
Also:
I do this. Not very often, but it happens.
You're right. Reviewing my feelings on this I discovered that my main "ugh, that's terrible" feeling comes from the observation that a correlated set of people form a control system that wipes out the contributions of others not in a similar or larger implicit alliance. That doesn't imply the solution is to vote independently of the total, though, as there are negative side effects like the one you describe.