Also, any software tool that can be removed by someone else is broken by design. But yeah, maybe that's why there aren't any useful tools for using Twitter :(
Simple. There's people agitating for free speech on idealistic terms, and then there's people agitating for free speech because they have an agenda and want a captive audience.
You can even see it in this comment thread. Take a look around and see if you can find any greyed-out comments that are arguing against the pro free-speech crowd. Down-voting is censorship via mob rule, so that should be twice as distasteful, but yet you see greyed out comments. The folks doing that are the latter, and not the former.
I don't want filtering that's imposed by sites or their users. I want filtering that's implemented locally. I'm OK with opt-in filter lists, such as those used by ad-block extensions, as long as they can easily be customized. But I'm not OK with server-based filter rules that prevent me from ever seeing stuff.
On HN, I have "show dead" enabled, and I occasionally vouch for dead comments.
Edit: typos
You generally gravitate towards down-voting unhelpful, out-of-place, or in some way inaccurate content not simply content you don't agree with, BTW. More often than not I see comments start to turn grey because they miss the point and/or aren't really useful contributions to the discussion. Good points, despite the position being argued, tend to remain opaque.
If one fails to stay within the boundaries of HN's Overton Window, you run a high chance of being rate-limited for "starting flame wars", regardless of whether you were the one who actually started it. What comes after that I'd rather not find out so I try to keep my opinions to myself as much as possible. Whether downvotes are used to detect instances of dissenting opinions is unknown, but it's one of the most obvious ways to discover it I'd think.
> ...not simply content you don't agree with, BTW
You do not actually know this, it is a heuristic prediction. Even getting a half-accurate feel for that would require access to voting data and a lot of time reading over downvoted comments.
People often do not even know why they themselves are doing many things, such is the nature of the human mind, that evolved to optimize for speed over accuracy.