I think just a basic minimal amount of moderation would solve 99% of the problems.
#1) Posting anyone anywhere's contact information = ACCOUNT BAN
#2) Accusing anyone anywhere of criminal activity = ACCOUNT BAN
#3) Threatening anyone anywhere with violence = ACCOUNT BAN
#4) Multiple accounts = ACCOUNT BAN
#1)
- does that include posting a link to somebody's facebook account?
- what about cases of escrowed contact information that should be published?
- what about posting a company address for complaints etc?
#2)
- what about accusing someone of a legal activity in their respective country that would be illegal in the posters' country?
- what about pointing out that a certain activity could be considered illegal under certain circumstances?
#3)
- no questions about that, but I could imagine that to be a slippery slope as well.
#4)
- outright no. That's been thoroughly discussed and it is "forum moderation consent" that multiple accounts are okay.
The point here is, it's really difficult to find a golden set of rules for a global community with different views, beliefs, legal systems, and cultural backgrounds. Things may look clear for you, but they most likely won't be for everybody else for any given case of the above.
I still propose the market solution,
make vendors pay for "vanity forums":
https://bitcointalksearch.org/topic/m.3011400That would probably solve the problem once and for all.