If we take the classical position that words point to real things in the world, "useful label, loosely agreed to out of convenience" is kind of just regurgitating the meaning of "word". The first half indicating the function, and the second half accounting for the fact we live in a world with a continuum of linguistic disparity.

Now, this position isn't the only position. But a relational model of language for example takes his assertion to an even more extreme place, and suggests they don't function as labels at all.

Metre.

"Car" is a good example of a label that's pretty strictly agreed to. If someone tells me they've developed a new car and then shows me a motorcycle, it's easy to prove that it's not a car, even though many of its engineering principles and functional components are identical to those in cars.

With consciousness, on the other hand, there doesn't seem to be any motorcycle-equivalent. Essentially everyone I've discussed the issue with (myself included) expects that any mind which runs on similar principles to ours or has similar thoughts to our thoughts is conscious.

Like non-referential nouns?