Apart from you apparently not being able to delete your Threads profile, it contains similar metadata spying clauses that the other Meta products do about all sorts of metadata that can be tracked and passed upstream to Facebook and Meta (the reason why I deleted my Instagram and Whatsapp accounts years ago).
We've seen before though from Facebook, that it does not stop with "using the information to improve our offerings to you", and that the information also gets passed to 3rd parties ('partners') as well. Meta is also based in a country famed for its data collection.
Your metadata is data collected that is not related to the information you consciously put in your profile, posts, and comments. It includes your location throughout the day, your contacts, WiFi and Bluetooth connections, search history, purchases, when you are active, and importantly specific identifiers for your device (so that this behaviour can be matched to data collected by other 'partners'). This all starts to build up a pretty valuable profile about your behaviour outside of the app.
I also collect visitor data on my website (and did a video about it showing what I can see), but I use a self-hosted open source service, the data does not get sold or given to anyone, and I only aggregate the data to determine what pages are popular, what search terms are finding my site, etc. I'm not profiling people or selling data to 3rd parties.
So, although I love testing out new social networks (and use about 17 at any time) I won't be touching Threads. But if you're a Facebook, Instagram or Whatsapp user, this really won't interest you much as your data is already sucked in.
I know many in the Fediverse won't like this, but I will consider reconnecting to some Meta users once Threads gets ActivityPub support. The reason is that all the behaviour side information is safely on a non-Meta app. All Meta will see is who I'm contacting on their side, and what I message to them through the open protocol. There is nothing stopping anyone already doing that through the ActivityPub protocol. However if Meta finds some devious way of inserting adverts (or anything else) into that connection, then I'll once again isolate myself fully from them.
I've long been on Mastodon already as my Twitter alternative, and over the last few months especially it has matured well in terms of a richness of information and news, meaningful interaction, and also working through its moderation controls that you can execute yourself.
See
Threads, Meta's Twitter rival, is tracking you in all sorts of ways#
technology #
privacy #
Threads #
metadata #
socialnetworks 
All your data is belong to Meta.
