Of Juggernauts and Semaphores

I've always considered writing to be like a jigsaw puzzle. The correct word fits exactly, tessellating perfectly within a sentence to create a precise image or idea. A wide vocabulary makes the task easier and the final product both clear and concise. But "therein lies the rub" (to quote someone who invented words if nothing else fit well enough). Language is a strange beast. Using a common word that isn't quite precise can alter meaning, but using unfamiliar vocabulary invites even greater risk.
When I started this blog, my husband (the English teacher) denigrated the title. "Liminalesque?" he said, "No one will remember that. No one can spell that."
He's probably right; sometimes I have trouble spelling it, but it says exactly what I need it to say.
Not long ago, an editor/friend critiqued one of my short stories, criticizing my use of the word "coruscating."
"You can't do that," she said. "People won't understand you."
I beg to differ. People won't understand me if I don't use the right word.
Coming across new (to me) vocabulary is one of the joys of reading, but in the cutthroat world of trying to get an agent, let alone get published, could vocabulary be a deal-breaker?
My most recent comeuppance was in my writing critique group. I will admit that for a YA short story, the words "juggernaut" and "semaphore" might have been pushing the envelope a tad, but they are such glorious words. Still, I've been told that if I'm writing a bildungsroman (oops--make that a coming-of-age story), I should have the protagonist (sorry--main character), use age-appropriate language. Does this limit me to "awesome," "shit," and "OMG"?
I think not.
Last week, I was sent to the dictionary by a high school student who used the word "irenic" in a long, complex poem imbued with gorgeous language. It was not a misspelling of "ironic"; she meant what she said, and it is a word with which we should all make ourselves familiar.