Is there an online reference resource devoted to commentary on the finer points of usage, connotation, and word choice in English?
(E.g. what nuances/shades-of-meaning/usage considerations would inform the choice between "firmament", "(the) heavens" and "(the) heaven"? or between "spry" and "lively"? etc. etc. I'm thinking of something in the spirit of the usage notes sprinkled—sparingly, unfortunately—throughout the M-W's Collegiate, but more extensive and up-to-date.)