For (Michael) Jordan, we often see Jordanesque. Why? Perhaps because he is His Airness (and the -esque suffix is associated with fanciness)? Maybe also to avoid confusion with Jordanians?
Plato -> Platonic. Why? Do names ending with an "o" generally get the suffix "-nic"? If so what do we do with Michelangelo?
And here are some for which there does not seem to be consensus:
Tolstoy -> Tolstoyian? Tolstoyan? Toylstoyean? Something else? Any guidelines?
Schelling -> Schellingian? Schellingesque?
Is this just mostly arbitrary and a matter of convention?