This is something that I was wondering about as well. I do not like Heal or Harm being based off of the characters current relationship with which point he uses without spending Strain.
I intend to suggest the following to my table when it comes up:
Heal is fueled by light side points.
Harm is fueled by dark side points.
Both options are available to ANY character with the power.
I just cannot justify, thematically, a light side follower in turmoil being UNABLE (not the same thing as choosing not to) to harm a living thing; or a dark side follower not being ABLE to heal another living thing without extra damage somewhere. Just because you currently spend dark side points without strain should not mean you cannot heal someone in need (I think The Force would probably WANT you to), likewise just because you currently spend light side points does not mean that you cannot cause pain with the force and fall faster to the quick and easy path...