For years, whenever I have made salsa, I dutifully peeled the charred skin off of roasted chiles before using. "The skin will make it bitter," I've always believed.
I few weeks ago I was making a salsa at my girlfriend's mom's house. Her grandmother saw me peeling the jalapeños and serranos, laughed, and told me in her charming Spanglish that I didn't need to do that. I took her advice and threw the chiles in the blender with the skins and proceeded.
I've tried that method a few times since and you know what? She's right. The skins add an interesting black color, smokiness, and, yes, a bit of bitterness, but it's GOOD. It saves a heck of a lot of time and tastes better.
On a similar note, I've also tried making a recipe from a Cuban friend that consists of blended roasted tomatoes (those skins removed), roasted garlic, and blackened chiles de arbol to which chopped cilatro, onion, avocado, and a squirt of lime are added. I've always been told not to let dried chiles blacken. But, again, that advice is wrong, this stuff is really good.
Now I wonder, is the ubiquitous advice "peel roasted fresh chiles" and "don't let the dried chiles blacken" just a result of the misguided belief among most Americans that Bitter = Bad?
No doubt burnt chile skin isn't always a good idea. Chiles rellenos come immediately to mind as one dish where they might be a bad idea. Sweet roasted red bell peppers, like the Italians make, is another exception.
But otherwise: try eating the black stuff!