Weird results indeed. I'm not sure if this is part of what you were pointing out, but plus and minus signs should be chainable. However mIRC is still getting the wrong values for some of the calculations you gave. ie.

Code:
$calc(1 -+-- 2) 	->  3 (should be -1)
$calc(1 -+- 2) 		-> -1 (should be 3)
$calc(1 -/- 2) 		->  1 (should be an error)
$calc(1 -/-- 2)		->  0 (should be an error)
$calc(1 ++--++-- 2)	->  3 (correct)
$calc(1 +++--++-- 2)	-> -1 (should be 3)
$calc(1 ++--++--/ 2)	->  0 (should be an error)


mIRC appears to incorrectly treat the additional plus signs with the same behaviour as if they were minuses, whereas they should all be discarded from the calculation.

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