Lemmy.ml has now blocked Threads.net
There is nothing they can do to fuck up your experience, ESPECIALLY on Lemmy though. Threads is a completely different concept from Lemmy and activity pub is well defined.
The only thing they could do is just not moderate threads and therefore putting spam in everyone’s feeds. That’s about it. I don’t think they’re leaving that unmoderated.
Someone correct me if I’m wrong, but it seems like it would be trivially easy for Meta to make an army of bot accounts to manipulate whichever posts they want into being near the top of people’s feeds. That could be regular ads disguised as normal posts (a la Reddit-style guerilla marketing), or even more political astroturfing.