Continuing the discussion from Posts on Forums seem to be down considerably:
There is a way to follow subthreads if people use the Reply button or quote a previous post:
Clicking “2 Replies” shows the two posts that replied to or quoted this one:
From there, you can select the down arrows to jump to the reply. From there you can follow other replies or jump back to the post you were just on using the arrow at the top:
If there is a useful subthread buried in a conversation, it’s possible for staff to pull that thread out into its own topic.