hi darius! A similar topic is Content, text/plain, and fallback behaviors for limited clients, which is focused on rich text support specifically.
In general, I think concerns of interoperability are always a concern for the community group. Even if it’s not a discussion about hard requirements, things like codifying best practices, hashing out general principles, and coming to consensus on guides to implementation are definitely things the process can help with. Overall, I’d recommend using the #activitypub topic—#software is designed to be focused on specific implementations.