The read status for a thread is not working as I would expect or it could be a bug.
Here is what I see while reading a thread the first time, not the last 25 out of 75.
Here is what I see when return to a thread form the read tab:
It jumps to 28. I don’t even see the post that is only partly shown in the first screenshot. I think discourse should err on the side of returning to a slight older post, that you might have read, because in the worse case you get a little context into the next few posts. Perhaps, Discourse should take you back to the middle post or the partial shown post minus 1.