a registrar will not care about random abuse messages that do not show clear illegal behavior or is not signed by any lawyers office
even if the domain get’s blocked, how long does it take to set up a new one? How long does it take to set up 100 new ones?
activitypub is by default very vulnerable and inefficient. Sources are not validated and the protocol does not have any mechanisms to protect itself from such attacks.
Seems you were wrong
For me the site is still online.