Does "you are looking good" use "are looking" as a copulative verb?

Solution 1:

Normally stative predicates are supposed to be incompatible with the progressive form. E.g., The car is red, not *The car is being red.

However, this is flouted in a special class of constructions generally referring to a person's behavior: You're being annoying, You're being dumb, etc., pointing out some temporary extreme of behavior. You're looking good falls into this pattern, as it suggests that the person appears, at the moment, more attractive than usual.

Yes, you are hitting on someone when you say that. Not a general rule about rules for linking verbs, just a special construction.

(Also, say "copula verb" rather than "copulative verb," lest people think you are hitting on them).