The YouTube app introduced an easily accessible comment section revamp in April 2020, but it looks like the company isn't happy with the current design anymore. YouTube is testing a few new looks for the collapsed comment section in the Android app, and some variations even allow you to post your thoughts without having to enter the comment section first.
The redesigns are all currently available in the wild, though we haven't been able to pinpoint them to exact app versions — they're all coming as server-side a/b tests. One variation shows a top comment with a field to enter your own words below it and a button that lets you view all comments next to it. Another redesign just switches out the expand icon with two arrows pointing up and downwards for a clearer "View all" text, and another gives you an option to post a comment without even having to look at any other thoughts shared by the community.
Top left: Current default look. Rest: New variations.
As Google appears to be testing these changes in the wild, it's hard to tell which one will make the cut. The most useful design is probably the one that shows you a top comment and a box to write your own, though it remains to be seen if Google's tests show that other versions lead to more engagement or not.
You can download the latest version of YouTube from the Play Store or over at APK Mirror, but bear in mind that it won't necessarily carry the new comment sections for you.