"so and so collided with you"
Any damage that you thought resulted from ^^^^ is the result of you being shot. Said another way, anytime you see the above message, it's informational only. If you recieved damage around that same time, you were shot and hit. Said a third way - if his FE detects a collision, any damage that's calculated to take place from the collision is on his plane - not sent across the Internet to yours. Only your machine seeing the collision from your point of view damages your plane. Of course, if he's firing when he slams into you, your going to see the "so and so collided with you" message at nearly the same time as he shreds your plane with his guns, and your going to ASSUME that the damage was from the collision.
And yes, sometimes a collision doesn't mortally wound a plane (everyone has had times where they "just squeaked by" another aircraft with a glancing blow - and their plane not been fatally wounded.) So if he lights you up, and then hits you with a glancing blow, you'll see "so and so collided with you", he'll fly off, and your plane will come apart.
From the bullets, not the collision.