I should have been more clear in my post - there are no times in the Prequels or TCW where Obi-Wan acknowledges Artoo or any droid as being anything more than an tool or appliance. Just because Kenobi interacts with Artoo does not mean he views him as anything more than a droid just like the thousands of others. The argument in RotS is simply to wind Anakin up. The Prequels and TCW don't make a big deal of it, but there are several points at which it is made clear that Kenobi thinks of droids as sophisticated spanners. Unless Artoo specifically identified himself as Anakin's R2 unit Kenobi would never be able to tell the difference and hether you like it or not, this is exactly what happens on screen.