Superb photo! And please, don't ever tell me your home address, because I will steal your coat
Because silk is formal and tweed is not. To be sure, ancient madder/gum silk is on the less formal end of silk, but it's still silk. From a texture and formality harmony perspective, tweed and silk are often enough in tension that they're the wrong choice together. Just the same way you run a much greater chance of failure if you wore a donegal tweed tie with a navy worsted wool suit.
That's not to say you can't step outside those conventions and succeed, but there's a much greater chance of failure. At least where I'm at in my development, I'm not at the point where I can directly contradict harmony and get away with it. YMMV.
Interesting, I hadn't considered it yet from the formal vs. casual perspective...
Three patterns today. Any opinions on the success, or lack thereof, of this?
Warning: Spoiler! (Click to show)
I like it, CM. Looks like a well executed traditional fit to me. As a non-American who isn't so familiar with these terms: is this trad, or prep, or WASP? What is the difference between those, if any?