Do you even understand what you wrote there?
The case of whether it should be -4 or 4 is solely down to whether you take the minus symbol to be the unary negative operator or a component of the number 2. Seeing that plain string in any programming language or on paper I would take the answer to be -4, and if it were down to that then I'd say anyone disagreeing with it is wrong outright. The only place where it's not so clear is the fact that mIRC has no numeric type and so, as several people have pointed out, a variable with the value -2 put into $calc() will behave functionally equivalent as the plain string whereas it would in 99% of cases be meant as a representation of a negative number.
I think mIRC's $calc() should be a little more advanced in it's parsing and treat input from variables as if surrounded by parentheses. Scripters who wanted to override this behaviour could always use evaluation brackets.
