Is that because Safari doesn't implement everything decided by the standards bodies or because Chrome deploys their own features? Probably a mix of both, but eventually there is a convergence.

Things work surprisingly well in modern times. I'm not sure when you started using the web, but back in the 90s/early 00s, the situation was a lot worse then it was today, and the browser standards are probably the biggest collaborative achievement between corporate entities in the modern web-driven world.

> Not sure that’s the model to follow. Fundamentally though chat is different - where would the messages be stored for example? Who will guarantee deliver ability?

It might seem fundamentally different on the surface, but I think not. Just like the browsers doesn't handle where the resources it loads are coming from, messaging services can be the same way. Think IRC, or even your own example, email. As long as there is a user-agent where services look consistent, the situation would be drastically improved.

> Email is federated and has all of these things but sucks and so everyone made their own thing. I’ve yet to see evidence this just wouldn’t regress to email again

Email is another great example of a success when it comes to this. Yes, email has it's warts, but you can essentially sign up for any provider, or even create your own, and receive/send emails to any of the others ones.

I don't see "email" as a regression compared the IM situation we have today. Imagine you would need a gmail account to send emails to gmail users, yahoo account to send emails to yahoo users. That would be awful! But you're right that email could be a lot better, but still, I prefer it to the alternatives from the IM world.