The media overlay attributes that expect a fragment identifier say they require: "a fragment identifier that references the specific element as per the [XPTRSH]".

Is the reference to xpointer shorthand necessary here? If we were to actually follow XPTRSH we'd invalidate many potential ID references into HTML documents as HTML IDs no longer have to be NCName values.

Doesn't referencing XPTRSH also negate being able to use EPUBCFI?