Consider
x = -5
x =- 5
It's the same with +, just that we're not used to seeing unary plus in the wild.
I think you mean: x -= 5, which indeed is different.
Consider
now how about: One makes x negative 5, the other subtracts 5 from it. And under this design of the operator the only difference is a space.It's the same with +, just that we're not used to seeing unary plus in the wild.