When does it make sense to collapse threads in discussion?

When you have a threaded comment system, how do you decide whether you collapse replies to top level comments or no?

E.g.

Comment 1
    Comment 1.1
    Comment 1.2
    Comment 1.3 
Comment 2

vs some kind of collapsed threads (sometimes they show 1 or 2 of second-level replies)

Comment 1
   --Show replies
Comment 2
   --Show replies

This answer provide a great link on the topic, but it’s rather overview than actionable info.

Is there any sort of guidelines when it’s better to collapse thread vs to leave it fully open? Does it depends on the site type, e.g. news sites seem to show all threads open, and social media like Facebook or Instagram mostly collapse?