Tools from my experience...if it says:
You have collided, usually you take 100% damage, opponent takes none or minimal.
<> has collided with you, usually you take no damage, but sometimes will take minimal damage.
Or if both messages come up, both players are going to receive significant damage.
As for how the system decides who crashed into who, well, that's already been explained and is variable at times.
i think the shortcomming can be in each persons machine too.
in a collision i had with a zeek, i got the white ""XXX has collided with you" i look back, see him going down trailing smoke...as i almost enter a spin. i get control, and get shot down attempting to rtb.
watched the film....although i never got the orange""you have collided"" message, my film clearly showed the collision. so, although i only got the white message, both of our machines saw it, thus we both suffered. he wasn't shooting either, nor was i.