Even in Kyoto

I weigh 270+ and I don't break spokes, although I have trashed a couple of rear hubs. I ride 32h wheels on my Rivendell, just like you.

Did they use straight gauge 1.8 (15ga) spokes when they build your wheel? Maybe the spoke tension is just too high? Or maybe they used 2.0/1.5/2.0 (14/16/14 ga) butted spokes and they're just too fragile for loaded Randonneuring?

You'll know if you have straight gauge or butted spokes just by pinching the spoke between two fingers and then running those two fingers up and down the length of the spoke. If it's a butted spoke, you'll be able to feel where the width of the spoke transitions from one width to another.

You can get a cheap pair of calipers to measure the spoke at HomeDepot, I paid $7 for mine. They have expensive fancy ones, even electronic, but my cheap manual calipers work fine.