Is there really a formal, or at least commonly accepted, definition that excludes shortened lever action rifles with (or without) certain features from being carbines?
A manufacturer is free to call their guns anything they want, regardless of existing conventions, so I'm not sure that what a manufacturer calls a particular model of firearm is conclusive evidence.
That said, I suppose if all the major levergun manufacturers all agree on a definition/convention, that would be pretty telling. Is that the case?
After reading through this thread, I've been trying to find some source that has an official definition, or even talks about a common convention involving the presence/absence of features like half-octagon barrels, crescent buttplates, saddle rings, banded forearms, etc., and have, so far, been unsuccessful.
I also can't find anything that mentions a special definition or convention regarding carbines applying specifically to lever-action firearms as opposed to the more general definition of 'carbine' which includes virtually any short or shortened rifle.