What is the rule regarding comma usage when but is used between two contrasting adjectives or adverbs? It is a vey interesting, but stupid question, and one that I have had a hard time finding a definitive answer to. Or should that have been "very interesting but stupid question" or "very interesting, but stupid, question".
Since a comma is sometimes used to introduce contrast, my instinct would be the way I phrased it the first time, but I can't seem to find a definitive rule on the subject. My own opinion on the subject seems to change with either my mood or slight nuances in the particular sentence, e.g., if the adjectives/adverbs are before or after the noun/[verb/adjective] or if the but seems particularly parenthetical.
A few more examples taken from the web, illustrating inconsistent comma usage for similar constructs:
1A) In case of a fire alarm, please exit the building quickly but calmly.
1B) It was time to quickly, but calmly get out of the water.
2A) Water is an overlooked but essential nutrient.
2B) Carnitine is a hard-to-classify, but essential, nutrient.
3A) This is one challenging, but invigorating climb.
3B) This is a painful, but invigorating, process.
4A) Maidan remains occupied, but eerily quiet.
4B) “Star Trek Into Darkness” is a fun but eerily familiar Star Trek adventure.