It's basically just Internet trolls registering Twitter accounts behind proxies and saying the edgiest things they can think of to stir the pot.
This is misogynist male supremacist terrorism. Twittering threats of violent sexual assault is like phoning in bomb threats - even if you don't have any explosives, the communication itself is an attack.
High profile accounts could opt in to this moderation for tweets that @them or DM them.or whatever.
Two points:
1) Except when it isn't. 2) Isn't that enough? What are we, robots? It's true that some people might be able to treat the two things the same and not be affected, but they're a tiny minority. Harm is harm, even if you think that everyone should have thicker skin.
Just curious, because it looks like you're trying to be more transparent and I applaud that.
I don't understand your question about retroactiveness; can you explain?