Agreed the cross posting is much more visible and irritating. Not sure it will ever be resolved as it is a fundamental architecture design of the Fediverse. I would hate to see another closed source site be the main alternative but Squabbles is growing fast and with the new app looking so good it may accelerate its growth. Time will tell.
Fediverse
This magazine is dedicated to discussions on the federated social networking ecosystem, which includes decentralized and open-source social media platforms. Whether you are a user, developer, or simply interested in the concept of decentralized social media, this is the place for you. Here you can share your knowledge, ask questions, and engage in discussions on topics such as the benefits and challenges of decentralized social media, new and existing federated platforms, and more. From the latest developments and trends to ethical considerations and the future of federated social media, this category covers a wide range of topics related to the Fediverse.
I don't think the architecture has anything to do with it. The algorithms just need improving.
Even if it just shows the post with most activity once, links to other communities versions inside with comments. Uniqueness determined by url and or title similarity.