I agree that I also have been unable to sign message from address which I hold in my blockchain wallet. Do you mind sharing screenshots of your conversation with 2double0 publicly or maybe share with someone trusted (i.e actmyname if he doesn't minds)?
Why not you bro? You too are a very trusted member of the community as per I see.
I can share the screenshots of the telegram conversation with you via PM. Let me know if you are willing to verify it.