is the public bitcoin adress (which you will get from bitfunder) the one in "Settings" ->
"Public Bitcoin Address
This is YOUR bitcoin address. How do I deposit?
This address is displayed in public view with your holdings."
?
Yes.
Can someone point to how to sign a message in an address, please?
I've created new recive address in my wallet and copied to bitfunder. I think that's the only way you can be in full control of an bitcoin address.