The "scratch" language? I'm guessing it's an alphabet inspired by the scratches a feline makes with its claws. Sounds interesting, but I have to wonder, did the writers for TAS really go this far with the character or her species? I'm not refuting the notion, but this is the first I've ever heard of it. I thought the only thing worked out was the brief "bio" sold through Lincoln Enterprises which I suspect came well after the conclusion of the animated series.
When you think about it, the only thing we can determine from "on screen" evidence is that M'Ress is an organic lifeform since nitrous oxide and Mudd's "love crystals" affected her similarly to the way the chemicals affected humans. Really for all we know, she could have been a genetically "uplifted" lifeform (a "Moreau"), a human into extreme
body modifications, or a "victim" of a bizarre transporter accident.
I just figured she and Arex were little more than "walk-on" characters taking advantage of the animated medium to drive home the idea "these humans are in really deep space working alongside aliens". Basically, the initial reason for Spock's creation, but taken to the next level. But given the expected number of episodes they'd get to make (this was years before the advent of weekday aired cartoons comprised of 65 episodes) and the short running time (22 minutes without commercials), I just assumed the creators would not have bothered to create detailed histories for "cameo" aliens.
Though I'd love to be proven wrong (I mean that earnestly without sarcasm). Can you elaborate?