nobody is refusing to offer their sevices on linux because it is vulnerable
That’s not quite true, though in that case it’s about the service provider being unable to verify that the user isn’t running a operating system configured or modified to work against the interests of the service provider.
It seems to me software designed to facilitate discussion shouldn’t have a downvote buttton. There should be a UI for marking comments as inappropriate, but it should require a second step saying why. Perhaps one of the reasons should even be “I disagree”, but that option should have no effect.
It’s not impossible to abuse of course, but it nudges people in the right direction. Those UI nudges can be pretty effective.