How's your project going? Are you finding any tradeoffs you made stand out as especially worthwhile or something you'd choose differently if you started over (perhaps something you're planning to change)?
This suggestion seems to be a bit different from what you implemented on piedfed. I'm having trouble articulating it though. Something more like a feed of user defined subset of subscribed communities/topics.
AT protocol doesn't federate the way ActivityPub does. There are separations between how your dat is stored, how it is aggregated, how it is filtered, and how it is displayed. Each part can be hosted separately and federate differently with separate instances of each part. The aggregation part is the thing that is most critical and there are probably some limited independent instances of that, but BlueSky has offered no support in facilitating this beyond making their peices AT Protocol compliant. You van take what BlueSky built and try to run your own instance of the aggregation service but they provide no documentation or support. You could also build your own, but that's difficult and I don't think anyone is trying.
So it is federated, but pretty much no one is interested in doing the work to federate with the primary infrastructure.
The default UI is how most new users will experience interacting with lemmy instances at first. So it's helpful to create a better first impression. To the extent that this is built into the project itself makes it easier for other UIs to be created and maintained too.
I believe that the Lemmy devs are working on a better url scheme for posts and comments as well. This will also make it less annoying without any browser extension, script, or other third part service.
However, I want to encourge you to consider softening up your replies to people who you don't have a strong prior social connection with. I've started making an effort to do that and I've found that I'm having more rewarding conversations now.
That's very different from what I think people generally want by default, which is that when you're on lemmy.world, it's because that's your home instance and any links to other instances would be automatically converted to the lenmy.world version of the post or comment by default (as long as the two instances are federated).
Anyone that wants more could find a browser plugin or script, but every new user with an account of any instance would have an initial experience that's much less confusing and more consistent and pleasant.
It's not implimented because the developers of lemmy have been prioritizing other issues and features. They say they're open to code contributions, so someone would have to volunteer to do it.
https://lemmy.world/c/modlog exists