Vitor explains that they can see the length of time spent lookinh at a post, that you are typing etc. Gives me tik tik spy vibes. Posting is public and I choosr to do so. A part of why nostr is originally attractive was the idea that the relay was dumb. I do not wany relay operators compiling data on users without their knowledge.
Discussion
Now you have the knowledge! 😜
Probably from timestamping the requests you make to load posts from your timeline.
Time between request to load post A and post B is time spent on post A.
Could be avoided by loading posts in aggregate. Like 10 or more at a time. Then you just know that this time was spent looking at the 10 but not which specifically.
Also it could be, that the user switched apps in between.