Since this payload is written as a string in event.content fied. it follows the NIP specification. However, there is a risk of duplicating the kind of the event so a new proposal may need to be made on that point. Thanks for your comment.
Discussion
Are those meant to be replaceable events?
Yes. This payload may be replaced in the future.
Maybe try the new kind 30023?
I am sorry. I was mistaken. I only meant that there is a possibility that the specifications may be changed, not that the content of the event will be changed.
In Nothello, events (not likely to be changed) are added as the game progresses.
But it would be interesting to develop a game using the NIP-23 specifications.