Anything bad in the title or comments about Microsoft or IE results in automatic upvotes regardless of content.

Do you have a reason for that observation? I agree with it, but I don't have a good reason. People of pro-microsoft opinion often cite the relatively tiny numbers of Mac, Linux, etc users all the time, especially when giving rationale for staying on Windows, or giving a reason for why Windows attracts the most malware.

But you can't have it both ways: if there's only a tiny minority of non-Windows people, they won't have the juice to generally influence Microsoft-related article's ratings. It you want to have it both ways (Windows dominates to the exclusion of everything else AND those pesky Linux/Mac/whatever users are everywhere, upvoting critical articles), you've got a world view with a very basic contradiction at its core.

So: are there more Mac/Linux/Minix/LoseThos users, or do even the Windows users generally dislike Microsoft?

Just because there are far more Windows users than Linux users (not that that has ANYTHING to do with this, lots of Windows users use Firefox for example) doesn't mean the minority group won't be able to massively upvote something out of control. It's not like everyone votes, only a small minority vote - and guess who are more likely to vote? People who feel strongly (for or against). So if there are more haters than there are people who care to fight the haters, guess who "wins" the vote?

I suppose that I'm assuming some kind of proprotionality in upvoting or downvoting, maybe even two varieties of proportionality.

First, I'm assuming that Windows-users are represented proportionally with the general population in the Hacker News population.

Second, I'm assuming that Windows-users and Linux-users would be equally inclined to up- or down-vote any given story. That is, the proportion of voters (your "small minority" that votes) is the same in Windows-users population and Linux-users population.

Your point about Haters vs Haters-fighters is well taken.

I would imagine the average hacker on HN would be more anti-Microsoft than your average man on the street.