Hmm, but what would be the proper planet for the Addams Family to have settled with their mech as neo-feudalists.
Belladonna, in the FedSuns.
Back on topic, I would expect noble houses to use mottos with Latin, Greek, their current language, or their (adopted?) ancestral language. For example, I wouldn't be surprised if the original noble houses on Skye and Donegal used Gaelic for their mottos.
I would still expect to see mottos in the Draconis Combine but they'd be more like creeds than something to hang under a coat of arms (or, for the Combine,
mons).
Would House Cameron's motto be "The Inner Sphere is not enough."?