I contacted support about this about a month ago.
It appears the default value of the Excluded XHTML filter URLs should actually be "/" (look when you make a new site using the corporate template), but isn't getting set to this on the empty templates.
This is how the setting should be.
And actually, it should be good for speed since the filter doesn't have to operate on any page.
The only downside is that you have to have valid XHTML.