Communication is a rather complex matter and having any single party decide what a given message is supposed to mean misses the point (see for example https://en.wikipedia.org/wiki/Four-sides_model).
Even simple societies end up appointing judges (impartial or not) to provide an outside view on a conflict, instead of letting the participants decide on any claim's merit.
twitter _does_ have a definition to work with, referred to from their ToS (https://support.twitter.com/articles/20169997-abusive-behavi...), which sounds pretty clear and simple to me and covers most if not all of what femfreq cited.
So this sounds like "merely" a compliance issue on twitter's side.
If someone is stabbed, do you require empirical measurements of their injury before you accept their pain?
Now, it's hard for me to imagine a less threatening interpretation of "Someone will rape and kill you" (to paraphrase most of the femfreq collection) than what the average person would make of it, but the rule I responded to was made a general assertion.
If the victim defines its status universally, the best way to live is to shut down all communication, since the sender has exactly _0_ control how things end up being received.
"The victim defines it" means that a simple "hello" can be considered abuse. Given the right circumstances, that might even be true (to stick to the theme: stalker contacting victim), but western society (that twitter probably subscribes to) doesn't typically hand out sanctions without having a third party determine the circumstances. Taking your the stabbing example, accepting the pain (and calling the ambulance) is one thing. Throwing the assailant in jail has a higher standard.
The discussion is about sanctions which are closer to the latter than "accepting their pain".