This is conflating two separate concerns: a private company can do whatever it wants with its own user handles. Sell them, seize them, delete them. Impersonation, on the other hand, can be challenged in the court of law.
Twitter will certainly prioritize the sale of short handles, single word handles, common name handles, and not something like @apple (just because of the volume of squatted and unused handles that can be easily monetized). If they seize and sell @apple, and the new account will impersonate the company Apple - that's a totally different legal situation. If the sold account will just post pics of apples, I don't think the crime of impersonation would be relevant.
Twitter will certainly prioritize the sale of short handles, single word handles, common name handles, and not something like @apple (just because of the volume of squatted and unused handles that can be easily monetized). If they seize and sell @apple, and the new account will impersonate the company Apple - that's a totally different legal situation. If the sold account will just post pics of apples, I don't think the crime of impersonation would be relevant.