Trying to reconstruct the name of a science fiction/fantasy story. Earth had discovered many, many populated planets. Protagonist works at an embassy at one of these for an embarrassing figurehead ambassador-type. Aliens on planet eat wood (and make woodcarvings with their teeth). Embassy introduces idea of Martin Luther King day, aliens discover concept of free speech and want to practice it, but king (?) doesn't like it, and has quills of aliens cut short when they say things he doesn't like. Protagonist tells aliens that someone once shaved her head when she said something she didn't like, so she painted it red. Aliens then decide to decorate shorn quills with fancy beads.
Marianne Tedesco is the Earth representative to the planet Rejoicing, and the embarrassing superior is Clarence Dogget:
Clarence Doggett was Super Plenipotentiary Representing Terra to Rejoicing and today he was dressed to live up to his extravagant title in striped silver tights and a purple silk weskit. No less than four hoops of office jangled from his belt. Marianne had, since meeting him, conceived the theory that the more stylishly outré his dress the more likely he was to say yes to the request of a subordinate. Scratch that theory
The Rejoicers eat a type wood called sweetwood and they also carve it with their teeth to make presents. The Martin Luther King holiday is however is the idea of the Marianne's friend Esperanza:
This time it's not my fault. This time it's Esperanza's doing. Esperanza decided, for her contribution to our round of holidays, to celebrate Martin Luther King Day. (All right—if I'd known about Martin Luther King I'd probably have suggested a celebration myself but I didn't. Look him up; you'll like him.) And she invited a handful of the Rejoicers to attend as well.
The bit about the head shaving is:
Marianne couldn't help but grin. She ran a hand through her pale white hair. "I've had my head shaved—that was long ago and far away—and it was intended to shame me."
"I painted my naked scalp bright red and went about my business as usual. I set something of a new fashion and, in the end, it was the shaver who was—quite properly—shamed."