A: You can limit who can send you DMs/PMs! You can also limit notifications!
B: You can also block a site entirely for yourself.
See attached pics for how.
2: Instance administrators:
If you don't want to block threads.net entirely, consider these options for your userbase's safety:
A: Between "Full federation" and "Suspend" there is LIMIT, which hides content from an instance unless a user either follows the user posting it, or searches for it.
B: There is also "Reject media," which means you never cache a remote site's attachments. This de facto makes all such content sensitive ("unavailable"), requiring an additional click to view.
