Registration - 2.1 - sector_identifier_url description

I think I'd remove the statement on requiring a TLS/SSL certificate check and instead reference where the concept is description. Something like...

A HTTPS scheme URL to be used in calculating Pseudonymous Identifiers by the OP. The URL contains a file with a single JSON array of redirect_uri values. Please see section 2.1.1 of this specification and section 2.1.1.1.1 of OpenID Connect Messages 1.0 for more details.