Hi Dan
No, I don't think there is a connection to 'In forums in "Moodle in English" last post is the first post for visitors!' https://moodle.org/mod/forum/discuss.php?d=270896. (Which is not solved in my view. Will write there later.)
But there may be a connection to this: "Posts no longer indented in long discussion threads on moodle.org" https://moodle.org/mod/forum/discuss.php?d=270878.
Anyway, to put the question in more general terms: Let's say there is a discussion thread in moodle.org, which has this tree structure once in drop down at the top "Display replies in nested form" is selected. Let's also say, person A starts reply to the last post in that tree and submits it at t=T. A person B has also started replying to a post at the middle of the tree and submits it at t=T+1. Then person A saw a typo and edited his post and submitted it at t=T+1.
The question: Which post would you expect to be shown at the last post in the forum overview?
I would say the post by person A. From the example I gave earlier, you can see that moodle.org shows forum post B as the last post in the thread.