I would think (though I don't run browser certs/rules) - that a domain.com - is valid, whether you are going to
subdomain1.domain.com - or subdomain2.domain.com - and a web publisher would have every right to move you from one to another "freely".
I understand frames and some parent doms can't reach "across domains" - but subdomains? unsafe? questionable?
Sounds like another set of "laws/rules" we don't need.
The question becomes "Do you have to turn off Opera security to get it to work right?"