I don't know why discussions of free speech always treat it as a binary, where we have it or don't. As a practical matter, banning Nazi hate speech as Germany does, doesn't mean Germans have no freedom of expression, they just have less, if what you're measuring is the number of topics on which you may freely express yourself. On the other hand, if you measure freedom of speech by how many can exercise it, you might come out ahead by preventing Nazis from holding rallies, since their rallies have an intimidating effect. If your goal is to maximize freedom of expression (as it should be), then you should be considering who's prevented from expressing themselves.
HN is a great organic example of this: the moderators here have been cracking down on abusive behaviour for a while now, and this has had a positive effect on the discussions, which are more polite and seem to have a lot more participation from a wider segment.
Except that I've seen legitimate dissenting opinions routinely killed on HN threads, because they go against groupthink.
Maybe more people participate, but we're just seeing more of the bulk views, not more diversity of viewpoint, because the people joining are moderates with common views.
I, personally, want to optimize freedom of speech to give me the most diversity of exposure -- something I think more aggressive downvoting and moderation stifles.
HN is a great organic example of this: the moderators here have been cracking down on abusive behaviour for a while now, and this has had a positive effect on the discussions, which are more polite and seem to have a lot more participation from a wider segment.