Well in this case, the original author was relying on '0' == 0 for their code to work. Even if you were dead set against using strict equality (which is silly, but whatever), the code is still disingenuous and should have tested index == '0' to make its intent clear. There's no other value that they could have being relying on it to coerce without some other very nasty things going on.

> overzealous developers might accidentally break your code trying to be proactive

It's not just people changing your code, it's people trying to read your code (including you, months later).