Why does operator ++ return a non-const value?

Question

I have read Effective C++ 3rd Edition written by Scott Meyers.

Item 3 of the book, \"Use const whenever possible\", says if we want to prevent rvalues f

Answer 1

If it is non-const, I expect *(++it) to give me mutable access to the thing it represents.

However, dereferencing a const iterator yields only non-mutable access to the thing it represents. [edit: no, this is wrong too. I really give up now!]

This is the only reason I can think of.

As you rightly point out, the following is ill-formed because ++ on a primitive yields an rvalue (which can't be on the LHS):

int* p = 0;
(p++)++;

So there does seem to be something of an inconsistency in the language here.