@SomeoneElse
There is no change if my reply is to the currently most recent in the thread.
Mostly I explicitly chose to reply to a specific post (99%)
and only rarely reply generally to the thread (1%).

It worked always for me in the past (up to and included October 29th) - as far as I remember.
That is why I think this a general issue / bug (since November 1st → I have looked this date up in my profile a minute ago).

I hope there is a fix for this issue.