[dukoid]

In some countries (such as Germany), a comma is the official decimal separator -- so v += 1,5 will look quite innocent...

[einpoklum]

That's a valid point, but

v += 1.500

may be just as confusing.

[thebruce87m]

A valid point. Nice.

[anoncake]

Only if you forget whether you're reading German or C++.