Overview
As the attached screenshot shows, occasionally there may be cases where cuts with melee weapons (e.g. gladii, longswords) can damage an internal body part in a neighbouring section of the body while leaving the parent body part unscathed. An example is that a cut that originates at the right leg may damage the left kidney too, but the torso is left unscathed. This only happens occasionally.
It isn't human-specific either; this is reproducible with animals too. Again shown in the attached screenshot.
Update: This can also happen with surgery failures. I've only seen it happen with minor ones though, again a tricky one to catch.
Expected Outcome
If a cutting attack were to originate at one location and damage an internal body part in an adjacent location, the parent of that internal body part should be damaged too. Alternatively, don't damage the internal and just damage the external instead.
Actual Outcome
Parent body part of an internal body part which was injured by an attack originating at the adjacent body part is left unscathed.
Steps to Reproduce
1) Spawn two colonists
2) Have one of the colonists equip a cutting weapon (e.g. gladius, longsword)
3) Have the armed colonist attack the unarmed colonist
4) Observe - may take a few attempts to get a result similar to attached
[attachment deleted due to age]