Not sure you can strip more from it, but breaking the parts down may help you:
*i gives you the variable the reference points towards, so it's like an &mut i -> i conversion.
Rust doesn't have the x++ operator, so x += 1 is probably as far as you can go. It's basically sugar (although counts as a different operator) for x = x + 1, so if you can modify that expression, you can do anything.
I guess I had higher ambitions when I started the answer, but the *i turning &mut i into i is the main take away. And with numbers you can also do that to "unpack" it, since it will be copied automatically. A non-Copy type would not allow the same amount of freedom.