Jira 9.x has changed the way the comments are getting collapsed based on the preferred order:{}

Oldest first -> show “Load 10 newer comments” at the bottom
Newest first -> show “Load 10 older comments” at the bottom

Comparing to Jira 8.x, the behavior is:

Oldest first -> show “View xx older comments” on top
Newest first -> show “View xx older comments” at the bottom

We can understand that some users might prefer one or the other, the suggestion is to make it configurable, so the admin can choose which behavior they would like to have on their system.