Reflexive Comparison.—The comparative followed by the reflexive pronoun in the genitive is used to denote that an object displays a quality in a higher degree than usual. The degree of increase is measured by comparison with the subject itself. αὐτός is often added to the subject:
αὐτοὶ αὑτῶν εὐμαθέστεροι γίγνονται
πλουσιώτεροι ἑαυτῶν γιγνόμενοι
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].