Have you read the comments on Instagram? The vast, vast majority of comments and comment impressions are essentially just "+1" or @-mentions, typically used in lieu private sharing.

It's the 2020s internet equivalent of walking around a museum with friends, repeatedly telling them about an absent third party, "so and so would just LOVE this". It's an interesting form of signaling that I think Instagram has cultivated really well.

If you look at IG comments through this lens, ranking or sorting is basically unnecessary.