Andrew Barnert writes:
I’m not sure this example really argues the case.
To an experienced C programmer, both += and ++ are intuitive. But to a novice who’s never programmed, neither one is intuitive.
I'm sorry, I expressed my point poorly, which is, first, that IMHO your statement above is exactly right. In addition, I meant to argue that "+=" got in because as an assignment statement it is useful to express mutation in place, while "++" had no such use. It's an argument which is similar in form but along a different dimension from the one you emphasize.