I do snack on butter by scraping bits with a spoon. The salted stuff is delicious. But I'm good for a about a teaspoon and then I forget about eating.
But why does butter have to be nutrient dense? It has a nutrient: energy. You gotta burn something to live. I get enough vitamins from my regular meals, which is why butter is a "snack."
I do agree that bulletproof coffee should be a treat, not a meal replacement, and that you should budget your fat calories for it. CICO still generally applies to fat burners, kinda sorta.
5'0" female, 44 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Gained back to 115(!) on SAD chocolate, potato chips, and stress. Currently keeping food tracker.
I (try to) follow by-the-book primal as advocated by Mark Sisson, except for whey powder and a bit of cream. I advocate a two-month strict adjustment for newbies. But everybody is different and should tweak Primal to their own needs.