It would be entirely possible for Twitter to create various community driven feedback mechanisms, they just don't want to.
Plenty of online communities have various moderation systems, including HN that hugely reduce the potential for abuse, trolling and bullying - and most don't require your real identity.
They have community driven feedback mechanisms. When a user is flagged sufficiently often, they're pretty much gone.
Of course this is now abused against (some) X people and by (some) X people (for X being pretty much any cause or philosophy that creates uproar and with-us-or-against-us camps).
Plenty of online communities have various moderation systems, including HN that hugely reduce the potential for abuse, trolling and bullying - and most don't require your real identity.