For example, HN's front page contains a set of URLs for each item. This item would be https://news.ycombinator.com/b149012c-56f4-4859-82b8-1f3f83e... for one request, and https://news.ycombinator.com/73e78d90-cc25-4091-8ffa-94783a2... for the next request. Both requests would get mapped to the same page, and serve up the same content (except with another uuid inserted into links).
Every comment would go into a unique SHA1 bucket and never seen again.
However I do worry about moderation and trolls. Allowing people to make as much noise as they can is almost as damaging to free speech as censorship. I'm not really familiar with IPFS, what does it mean that unpopular comments disappear? Is it like seeding the only torrent (comments) that you like?
The thing is, to see that noise you would first have to be on the specific link, want to see comments on it, then go out of your way to install the addon if you haven't already. This is so much better for the people running the websites as they do not have to even acknowledge the comments' existence and are not obligated to moderate anything. Anyone who wants to comment or see them should know what they are getting into. They can grow a skin or uninstall the addon.
Is there any kind of rate-limiting to stop bad actors from making a million comments per second?
About the moderation, etc, this is really opt-in so you use it by your own choice and by "going in" you pretty much have to expect that like any other place where moderation is light or non-existent you'll see stuff you dislike.
Uploading to IPFS is like creating a torrent for any file you share. Someone always needs to be seeding that file for it to remain accessible to people.
So what OP meant by unpopular comments disappear is that nobody would be seeding them.