I perhaps wasn't *quite* as excited as you, but maybe it's because in the past 2 weeks I've heard or read "mooted" used correctly 5 times! (counting Grayling's all as one, once on BBC radio, once in Al Franken's Lying Liars [I believe], and the others I don't remember). And yes, I noticed, because it is so rare.
I confess however I thought moot had become analogous to "regardless" and "irregardless" (where people use opposite words for the same meaning) except here they used the same word for opposite meanings! I had no idea that "moot" as "pointless to discuss or debate further" was actually incorrect!
Actually, I was much MORE thrilled by Grayling's language in general. He used 2 words I'd never SEEN before and 1 that I had seen but had no clue what it meant.
Now about that piece of wood I've been staring at...