[gizmo686]

In my experience, mathematicians tend to drop the third dash.

I should also add that, as generally presented in higher level math, modular arithmetic actually does use literal equality. The abuse is in the numbers.

That is to say, when we write "9" in modular arithmetic, we mean the set of all numbers congruent to 9. In this case in "9=1 mod 4" the equality is literal because the set of numbers congruent to 9 is literally the same set as the set of numbers congruent to 1.