does this oy me belong to Sm 2750? The commentary (erroneously?0) attributes ou to the infinitive and not to the participle.
τὸν δὲ πρωτεύοντα ἐν ἕδρᾳ ᾐσχύνετο μὴ οὐ πλεῖστα καὶ ἀγαθὰ ἔχοντα παρ᾽ αὐτοῦ φαίνεσθαι.
While the participle (ἔχοντα) of course depends on φαίνεσθαι, it’s φαίνεσθαι (higher in the syntactical hierarchy) to which the ου applies. The μη is due to the negativity inherent in ᾐσχύνετο. So it means something like “He found the idea that the man in the foremost place of honor should not be seen to get the most goodies from him a shameful one." (Rather more convoluted in English than in Greek.)
Somewhat comparable (again αισχυν- μη ου infin.) is ὥστε πᾶσιν αἰσχύνην εἶναι μὴ οὐ συσπουδάζειν in the Anabasis (2.3.11), “so that it was a matter of shame to everyone to not share his eagerness” (so they did share it).
Holden’s commentary says that me normally negates the infinitive here and that ou is here abnormal, it strengthens the idea of unwillingness, He also mentions the same example from An, and also Rep. Lac c. 6 αἰσχρὸν ἐστι μὴ οὐκ ἄλλας πληγὰς ἐμβάλλειν does it mean it is a shame not to strike more?
Yes, there again the idea of shame (αισχ-) brings in the μή ahead of the ου. (“It’s shameful not to give his son other beatings.”) This seems to be Xenophon’s regular practice, and it’s in line with Greek usage in general.