The Planar Binding spell has no text excluding “obviously harmful” or “suicidal” instructions. On the other hand, all of the following spells do have such text: Command (1st level enchantment), Suggestion (2nd level enchantment, Compulsion (4th level enchantment), Geas (5th level enchantment), Planar Ally (6th level conjuration) and Mass Suggestion (6th level enchantment)
Under the meta-rule that “there are no hidden rules”, does this mean that the subject of a Planar Binding spell can be given a harmful/suicidal instruction?
I think that RAW, the answer is yes. I’m more interested in RAI and RAF, game balance, and how this helps develop an internally consistent “theory of binding magic” (search this site for “Planar Binding” for numerous other questions related to such a theory).