Deleting your Threads profile will also kill your Instagram account - eviltoast
It's come as a shock to many that they can't delete their Threads profile without also deleting their Instagram account.

  • Meta’s new Threads app is closely linked to Instagram, so much so that you can’t delete your Threads profile without deleting your Instagram account.

  • This is mentioned clearly in Meta’s supplemental privacy policy, which many new Threads users failed to read in full.