okay, syntax time!

Apply mending arms ---> does nothing

Apply mending right arm -> fixes either right OR left arm, regardless of which arm I apply it to

Same goes for legs

is this a bug? it's extremely odd to me

You should be using 'apply mending to arms' in any case.

You can't apply to specific limbs. You can apply to head, chest, gut, arms, or legs.

To clarify what the others are saying, the parser is ignoring 'right' and assuming it to be 'to'. So you wind up with apply mending to arms, even though you're entering apply meanding right arm. Likelwise you'll need to apply mending to chest, etc.

Ok, that makes sense. Thanks