With regards to harassment, Twitter suffers from the moderator-to-user ratio pointed out in the article but ultimately decentralization must deal with whack-a-mole on bad faith instances (plus all the other issues described).
I fear that this sort of system also has the potential to drive people even further in to social echo chambers where terrible ideas and behaviors can flourish in harmful ways.
There's nothing wrong with people organising and debating issues among like minded peers. The dysfunction of twitter isn't rooted in 'echo chambers', but in the lack of grouping, which results in a Hobbesian war of all against all.
The Facebook marketing idea of a global digital village without borders is a nice vision for a corporate brochure, but no way to actually organise human communities.
Alex Pentland did interesting work on social networks and ironically enough it was precisely hyper-permissive and connected networks that produced bad outcomes and echoing because the opportunity to copy and descend into permanent agitation is largest in systems that have no barriers or idiosyncrasies. A barrier free system is a group-thinking sytem by design because it works too fast
It's easy to see why this is profitable for the people who run the platforms, but it is of questionable social value.
That's half - and the less important half - of what an echo chamber is. That by itself is fine. It's when joined with the other half of "echoing so loudly" that any dissenting views can't be expressed and are drowned out. The group only hears what they want to hear, never having their ideas challenged. No matter how terrible the idea is they only tolerate other people who support their idea. It isn't just discussing things with like minded peers, it's actively silencing anyone who doesn't agree and not having any debate on the subject.
HN is an opt-out echo chamber. Dissenting views are flagged or greyed off the page for nobody to read, except for the people who turn ShowDead "ON" and opt out of the echo chamber. In return for seeing dissenting opinions they see a lot more spam, a lot more vile posts, a lot more noise. In many ways people would say that makes the experience worse, but I wouldn't have it any other way. If HN didn't have a ShowDead option I wouldn't continue to be here.
One is proper curation of the discussion forum. The other is building an echo chamber.
That's not an echo-chamber in the bad sense of the term, that's the basis for productive discussion.
Essentially, agreeing with the guy I responded to that an echo chamber requires silencing dissenting opinions without any hope of discussion.
I wasn't passing judgment on whether or not HackerNews is or is not an echo chamber.
If you browse through heated topics where the HN demographic skews towards one side of the argument, you can see the echo chamber at work simply by turning ShowDead to "On" and reading every comment on the thread. If you browse with ShowDead "Off" you might not be aware of how frequent replies are silenced for no reason other than not agreeing with the echo chamber.