regarding pointer operation in a printf function call

[Random832]

That last phrase may not be appropriate for a beginner-aimed
explanation either.

No, but it's important to get across somehow, or people will believe
that all they have to do is (i++,i)+i++

In any case, I'm curious as to what way you think Richard's implies
the opposite of defining a partial ordering.

It doesn't say it, but it doesn't say not, either, and the idea that you
can assign sequence points numbers like 1943, 1944, etc, might be read
as thinking "ok, first, there's sequence point 1, then after that,
sequence point 2, then sequence point 3" etc etc, all in a row.

It appears to be a pretty good, if thoroughly non-technical
explanation of it to me, which seems to have been the point. (Perhaps
*I* only think I understand sequence points.)

What I meant by "people who think they understand sequence points" is
someone who thinks (i++,i)+i++ is well-defined - after all, the first
i++ is before a sequence point.