[dragonwriter]

> In a UBI/negative-income-tax schenariom things like food stamps also shouldn't be cut off at a simple threshold, but instead factored in at your marginal rate.

In a mature UBI system [0], food stamps as use-restricted means-tested welfare wouldn't exist at all. (Food stamps in their original purpose as a system of agricultural subsidies might.) Their function would be rolled into the single benefit payment.

[0] transitional proposals often keep other means-tested programs during the transition, scaled back as UBI scales up.