Hopefully the title isn’t totally confusing.
When you read a thread to certain point on mobile (not sure about desktop behavior at the moment) and scroll back up a bit, a little arrow appears right on top of the read status bar in the bottom right corner. Clicking on that allows you to jump back to where you are coming from.
While this is most likely done based on the read status of the posts, would it be possible to have something similar when clicking the arrow on a reply post to get up to the post that it relates to? Having an easy way to go back down again would be extremely helpful, especially in longer threads.