the current workaround I’m using is to select “Settings” after choosing a blog. This shows the account details, and you can confirm which username you’re logged in under.
(The order of the accounts in the “Choose a blog” menu seems to be the order in which they were added. First account added at the top of the list, and last at the bottom.)

(Also if you’re editing on the BB Z10 – after editing, swiping down from the top of the screen brings up the action bar at the bottom with the menu buttons.
This wasn’t apparent as a new user of the device =:)