Thanks! I guess I'm not rendering replies published by Amethyst properly.
Discussion
There are 2 ways to do replies, the older and the newer way, see NIP-10: https://github.com/nostr-protocol/nips/blob/master/10.md
Some major clients still support the old way (Damus AFAIK), most newer clients go with NIP-10.
To be fully compatible with all, you'd have to implement both ways.