Any particle system without collision enabled, when pointed directly at the camera, will have sprites collide with the camera and slide diagonally off-screen like bird rolling off of a windsheild.

No culling setting or collision flags seem to affect it.

Also that the behavior is the same as when an in-editor user camera gets into a stream of particles, BUT, if the user is looking down or sideways at a particle system, he will see the particles pass right through the camera without being deflected.

2) How can we reproduce it using the example you attached

1 Open attached project
2 Open scene "Particle_CollideNSlide_Bug"
3 Just hit play and watch the game cam.

Here's all I do:
Create a new scene. Create a particle system with a box emitter so that the particles travel in a straight line, and have the velocity aimed directly at the camera.

reproduced on 4.2.0, 4.2.1, 4.2.2 and 4.3.0b4