Good Reason For Applying Buie's Planet Definition
Forget how it formed just define based on charcteristics. A Brown dwarf is a brown dwarf whether it formed more like a star or more like a planet as long as it acheived dueterium fusion. If it formed all by itself but never achieved DF it's a planet. Calling something a Brown Dwarf that never acheived deuterium fusion and is indistinguishable from an excaped planet doesn't make much sense to me.