I was a few seconds late providing review feedback on #5711 . It's probably easier to read my comments inline there, but I'll repeat them here.

1. Minor typo: corresponds
2. The spec needs to describe animation, specifically that it works the same as SVG paths since the shape syntax is a mapping to SVG path primitives. It should probably call out the fact that the curve operator actually produces two segment types, so it may not be possible to smoothly animate between two curves.
3. For that reason, I'd consider splitting cubic and quadratic into different operations rather than rely on the number of parameters
4. Similarly, a curve and smooth might actually be the same segment type as far as animation is concerned! Confusing!
5. I don't think via is a good term for bezier control points. The curve does not (typically) go through those points, which is what the definition of via would suggest. Maybe using is a better term?
6. In SVG syntax you specify the control points before the end point. Is there a reason this was not followed here? The rationale behind that in SVG is that the point specified last in commands is where the pen ends up (where the next segment starts).