@starhaze you mean 3? For 2. I would guess the best would be to allow for individual (also 3rd party) filters that then can block on any heuristic (new account, known harasser, keywords) - this should be under user control, but outsourceable, so either they build the filter themselves or they rely on a 3rd party filter service
@zauberlaus doh good catch yes i meant 3. and yeah you're solution for 2 i think is the right idea,sort of like the shared block lists that Twitter let people do?