Provided that a Third Party User is followed by or following a Threads account, Meta will ingest these pieces of data specifically:
Username
Profile Picture
IP Address
Name of Third Party Service
Posts from profile
Post interactions (Follow, Like, Reshare, Mentions)
So if you follow a threads user or even if a threads user just follows you, they pull all this data?
IMO this seems like reason to defederate across the board. Someone else can leak your info to Meta.