The main threat to your privacy induced by BitTorrent lies in your IP address being stored in the instance's BitTorrent tracker as long as you download or watch the video.
See the <x id="START_LINK" ctype="x-a" equiv-text="<a target="_blank" href="https://docs.joinpeertube.org/use-library?id=playlist">"/>documentation<x id="CLOSE_LINK" ctype="x-a" equiv-text="</a>"/> for more information.
This is just an extra information injected in PeerTube HTML that is required by Twitter/X. If you don't have a Twitter/X account, just leave the default value.
In theory, someone with enough technical skills could create a script that tracks which IP is downloading which video. In practice, this is much more difficult because:
An HTTP request has to be sent on each tracker for each video to spy. If we want to spy all PeerTube's videos, we have to send as many requests as there are videos (so potentially a lot)
For each request sent, the tracker returns random peers at a limited number. For instance, if there are 1000 peers in the swarm and the tracker sends only 20 peers for each request, there must be at least 50 requests sent to know every peer in the swarm