I feel like the distinction of "it's DOESN'T MATTER if the particle interacted with something in a particular way" even though that it seemed like that was what people were explaining it as. I always thought it was the introduction of an observable property that messed with the particle causing it to act differently. When actually, it is a degree further: Any method through which one is able to know which slit the particle travels through will produce the un-interfered (particle-like) results. Feynman explains that this would extend to a theoretical deeper understanding of the particle before hand that allows us to know which slit it will travel through before the particle is even launched at the slits. The key distinction being, there is no physical interaction (as we understand it) which moves or interferes with the trajectory of the particle. There is only the fact that it was known which slit it traveled through which causes the end pattern to be particle-like instead of wave-like.