Personally I think proposal 2 and 3 should happen concurrently. Using the example in the post I would setup a custom feed (that can hopefully consolidate cross posts) for breakfast. I would put [email protected] which subscribes to [email protected] I can also add [email protected] and [email protected]. so when someone posts about the best homemade peanut butter syrup recipe that is cross posted to my pancake and waffle communities, I don’t get 4 posts about it, I can see it once and choose where to reply (pancakes obviously, I’m a waffle purist).
Community interlinking/subscription fixes a slightly different problem than custom feeds IMO. It’s a really good idea, but I would personally still want custom feeds (with the ability to handle crossposts in a customizable way).
I think the community subscription model in the article fixes this (imperfectly). [email protected] can have strict rules while [email protected] could subscribe to it and pancakepurists could subscribe back with the understanding that the rules are slightly different there. [email protected] could similarly link to both those without either having to be mutually interactive.
I think the problem comes from some increased moderation loads by allowing a community to follow another. If I were to put on my paranoid hat it could be used to monitor and brigade a community. I think the solution for that is moderation tools. Banning instances, federation etc. I’m not a mod anywhere so I don’t know what is possible.