@hongminhee @julian I'm a true believer in RDF from back in the day, so I'm hardly neutral. But...

There are essentially no interesting ActivityPub extensions right now. Even Evan's chess example, no-one's actually using AP to play chess. It's just ActivityStreams + a few cute tricks now and then. Even if there were extensions, existing AP servers chop off and throw away data they don't understand. so none of these extensions could work.

I feel like most of the "WTF am I learning JSON-LD for" criticisms are coming from this status quo. That includes "if someone wants to add a gallery thing or whatever, can't they make a FEP?" The way things work now, your extension either a) works only in your software or b) has to be painfully negotiated with the whole community. We're all gonna have a big fight about it on this forum anyway. Let's not pretend JSON-LD helps us.

But if we add two things to the mix, the situation looks different. Those are 1. server software that "keeps all the bits", and 2. a whitelabel extensible app. That would make it very easy to spin up crazy new experiences for a sizeable existing userbase. Developers should not be forced to endure a FEP process, and they should not have to attract a userbase from nothing. They should be able to just build, without even worrying if they're stepping on toes. And of course, Fedify and libraries in other languages are a load-bearing part of that world, including enforcement of the JSON-LD rules.

That world does not exist at all today, but JSON-LD does, so it's pretty valid to describe this design as premature optimisation. I dunno though, we don't seem that far away.