I’m using a library named lemmy-bot. To achieve what you say, I need to modify both library and lemmy server. As you can guess, I can’t afford time for these 🙂
I think it’s not using much resources anyways. 2 requests per minute is nothing compared to hundreds of ActivityPub requests per second.
I didn’t tested non-followed community, but the bot works with mention event instead of comment. But still not sure, I’ll test this one 🙏