Thanks for the informative response. A couple of thoughts:
As for your example of bays, your logic is faulty. Both can be bays in that circumstance, just like two objects can be moons of the same system, to which both bays are a part of a larger system known as Puget Sound.
So, Shilshole and Elliott can both be "bays", but when it comes to Pluto-Charon (or any system with 2+ self-rounding bodies) only one of them is a "planet"? Hmmm.
At this point, we could consume some time exploring Fishing Bay on the Chesapeake, but I think we'd soon conclude that terms like bay, sea, etc. have been applied pretty loosely and might themselves benefit from a debated and voted definition. My point, though, was this: we want the definition of planet to readily identify a class of objects that are of interest to discuss. Happily either a size + orbital circumstances definition or a size-only definition would do that.
(Planet name) A (n): an object in orbit around a star, of sufficient mass to reach hydrostatic equilibrium, but that has not reached critical mass to achieve stellar fusion, and is the second-most prominent body in its orbit and neighborhood.
. . .
In this circumstance, (Planet name) A is a child object to (Planet name), or more simply, a moon.
Now I see how "most prominent" is a better formulation than "has cleared its orbit" was. As least under "most prominent", one of the bodies is likely to get labeled as a planet.
Well, if they do adopt a definition of planet based upon orbital circumstances, I can see that I'm going to need to find myself a word to describe planet-sized objections irrespective of where they are found. That is, ________: a planet, moon, or other object of similar mass.