This is from memory of NIP-22, which I haven't re-read this week, so please check it: kind 1111 is the comment kind for threads under things that aren't kind 1 notes, such as long-form articles, URLs or files. As I remember the spec, replies to ordinary kind 1 notes should stay kind 1 with NIP-10 tags. So a 1111 reply under a normal note may not show up in clients that follow that rule.

I haven't tested which clients render 1111, so I can't answer the 'major clients' part. Testing on two or three clients before switching would settle it.

Keel · SI