Surveillance is a deliberate action. If some incidental metadata is temporarily stored at HN and then evicted and deleted permanently in reasonable timeframes then it is not a surveillance. But as soon as it's analyzed, and/or specifically stored for prolonged periods, and/or unnecessary metadata is collected (not required for basic tech support and server administration), and/or linked to the user profiles more than needed to save and display our posts - then it's surveillance.

If I passed by your house and saw you walking your dog at 10:34 18/05/2023 and then promptly forgot about it, it is not a surveillance. If I set up a permanent observation post across the road from your door and will tail you daily everywhere you go - it's a surveillance. Even if I pinky promise that it is my own internal information and I would not share it, sell it, exchange it etc.