I emailed the makers of the Leonard Soil Knife, and two of their employees emailed me back Monday morning with many apologies. Apparently the tool I got was part of a bad batch involving poorly-tempered steel (and a lot of broken blades). They have since solved the production issue, and upgraded the tool with a few extra features. Having a job based in production, I know these things can and do happen.
They have mailed me a new one. All they wanted in return was a picture of the broken one. As a bonus, it’s the upgraded model!
I’m happy I’ll have one of these. I think in Texas soil it’ll be an indispensable wrangler of roots, rocks and rowdy weeds.