Okay, sure, but the underlying point is that the moderators of that community moderate all posts regardless of their origin, so biased moderators can direct the course of discussion. It’s more a problem for broad topical communities with polarizing topics.
Well, under this theoretical standard, you’d only be posting to a single community; you wouldn’t be literally tagging communities on your post. The hashtag comparison was more to how you view hashtags on Mastodon (e.g. you’re searching for a hashtag and seeing all related posts from every instance.)