Saud has hit it. Updating the character on Character and Roster doesn't affect their rank.
I should add a prompt on that page of the effect "You've changed the rank of a character owned by an account, would you like to update the rank on the associated account as well?"
----
The day Microsoft makes a product that doesn't suck is the day they make a vacuum cleaner.
That would be a really nice addition. I would suggest though that you only present this option for Characters that are not flagged as an ALT. But of course you probably already thought of that
.
----
Warlock - Lord Templar