No it's not. Moonlight is very much behind the curve and is always going to be playing catch up. They are a version or 2 behind depending on which features you look into.
Moonlight is only there so Microsoft can try to claim Silverlight is not some cheap proprietary solution to an nonexistent problem.
Same with Mono vs .NET.
The HTML5 standard is going to come in small sections. So instead of waiting for the entire thing, we'll get some portions as they work on it. And yes it does it have a set specification, it's just not done yet :
http://dev.w3.org/html5/spec/Overview.html
The video, audio and canvas tags are pretty much set though.
What's a "right" web application anyhow ? Silverlight is proprietary technology meant to lock you into Microsoft approved platforms. Like ActiveX before it. Stay away if you know what's good for the web (which if you are pushing Silverlight, you obviously don't).