> (a) Allowing something like <br></br>
There's legacy content that looks "wrong" if that doesn't render as two line breaks.
> (b) Allowing something like <a/>
There's legacy content that looks "wrong" if that's treated as an empty element.
And this legacy content starts with "<!DOCTYPE html>"?
I believe the standard should provide a parsing mode (and a way of triggering that parsing mode) that does not attempt to be 100% backwards compatible with bizarre and confusing browser bugs.
James