What Not to Wear's edict is that if you can't button a jacket, it doesn't fit and you can't buy it. Makes sense, but I recently thrifted a blazer that although it will button, it's a bit snugger than I'd prefer if I were going to wear it buttoned all the time. But I've noticed it looks a lot more flattering unbuttoned than most of my jackets, which look a little big when open and therefore are less slimming. Same with my cardigans, although it's less pronounced since they stretch.
Let's face it, I wear my jackets (blazer-type, not outer jackets/coats) open the vast majority of the time. Shouldn't I buy primarily for flattery in that case? Is it OK to buy things that are intentionally snug when buttoned, if you are not planning on wearing them that way very much?
What do you do? Do you follow WNTW to the letter or modify the rule?