ἐγὼ μὲν δὴ οἶμαι ἅπερ ὑπεθέμην ἀπειργάσθαι μοι.
I don’t understand why the commentary says that ἀπειργάσθαι is here passive. Does moi refer to the whole phrase or just to ἀπειργάσθαι ? that makes it an agent.
ἀπειργάσθαι by itself could be either middle or passive. Here it’s clearly to be taken as passive, with μοι dative of agent, normal with perfect passive.