The link goes to this users Mastodon post on the subject. I'm going to copy part of the text of his post without having to post the Threads post they were shown. Click through if you want to see for yourself, avoid if such things are upsetting to you.
"This was a post promoted to me from within Instagram to try and get me to use threads. Ill say that again: this is the promotional content shown to non-threads users as an inducement to join threads."
If you do click through to the Mastodon thread, you'll see several other people confirming they've seen the same or similar posts promoting Threads.
I've said the same thing in comments to other Threads related posts in this community but I'm going to say it again; didn't we create and use fediverse software like Mastodon, Lemmy, PixelFed etc in large part to escape the constant hate-baiting and algorithmic manipulation of companies like Meta? Why are so many in the fediverse prepared to throw their fellow fediverse users under the bus by exposing them to a company and a set of users who not only say these things and not only allow them to be said but actually use them as a promotional tool to encourage more people onto Threads?
If Threads was a fediverse instance, it would've been defederated from by just about everyone by now. Why are some people bending over backwards to give Meta a free pass?
'Wait and see' I hear people say. I can already see.