From a bug report: rogue's backstab bonus
(extra damage when foe is fleeing) doesn't apply when dual-wielding but
does apply to thrown weapons--unless both conditions apply. Having it
apply to throwing is too powerful. Elbereth makes it trivial to get
monsters to flee and a rogue with expert dagger skill can throw up to 4
of those at a time, so a level 30 rogue could get rnd(30) bonus 4 times
in a single attack. This makes the backstab bonus only applicable to
melee and polearm attacks.
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