Does he who curses "the lord of so-and-so" commit an act of apostasy by reviling the Divine Self, or is it necessary to pause to ascertain his intention, given the possibility that he meant the person himself or his mentor?

If the speaker explicitly states that by "cursing the Lord of the thing," he means the owner of the thing, and there is evidence to support his claim—such as a dispute between him and the owner of the chair or the room—then he does not commit an act of disbelief (kufr). However, if he does not clarify his intention, or if the context indicates that he intends to curse Allah, then he has committed a grave evil and may have disbelieved, because cursing Allah Almighty is disbelief. In summary, if the term is exclusively applied to Allah, then cursing it is disbelief. If it can be applied to Allah and others, then the ruling depends on the speaker's explanation, or on the contextual clues and common usage if he does not explain it.