A user checking out one of these URLs does not want to filter only local post on that instance.

I think it sounds like what you want is some sort of meta discussion / meta community / tagging construct. Per my understanding, that is planned, but low priority as Lemmy has bigger stability and scaling issues to resolve

On all instances, this url should mean “show me all /c/piracy on all federated instances”

I’m not so sure. What if I want to have a conversation on my private instance with only my friends who are on it about something piracy related? What if I would like to engage in the dbzer0’s discussion of piracy specifically since it’s the most technically advanced one, and also has some interesting social liberatory political views? I could get behind m/piracy showing all communities named piracy but I think I would want there to be a difference between my local comic book store, and comic con.

The current convention breaks the most important aspect of federation and makes its vestigial appendage.

What do you define as the most important aspect of federation? I define it as curated moderation. You get to pick the instances and communities that match your values. It makes your social experiences on the Fediverse more personal. This system doesn’t turn it into a vestigial appendage, and instead enhances it.

The current way has user asking question /c/piracy, but on which instance ?

If there is no @ symbol, it is local. If there is an @ symbol, it is on the instance after the @ symbol

So now they’ll all join the same instance .

They may, but they don’t have to

You wouldn’t post anywhere else since no one would every see it.

This is factually inaccurate and a misunderstanding

It’s a recipe for centralization.

I don’t actually think so. I’m on beehaw.org. You’re on lemmy.ml. We’re both having this conversation. It’s pretty cool. I have no intention of ever joining lemmy.ml, and maybe you don’t want to be on beehaw.org, but we can still find shared spaces here, on lemmy.world, slrpnk.net, and anywhere else we find common ground

I think this is obvious to most users

That’s true. We need to figure out how to better document this. This is a general problem with the fediverse at large, not just lemmy, kbin, or mastodon

were deal with “voat with extra steps” here

Could you elaborate? I don’t understand