How to reproduce:

1. Open attached project (softParticles.zip)
2. Open scene main.unity
- Scene contains a few cubes, a Particle System spewing black clouds to obscure vision and some text explaining the reproduction steps
3. Play the scene
- Note how the cubes have a pink outline
- Disabling Soft Particles or MSAA gets rid of the outline. The same is true when the Rendering Path is set to Deferred instead of Forward

- By Design: http://docs.unity3d.com/Manual/class-QualitySettings.html - Soft Particles fade out near intersections with other scene geometry. This looks much nicer, however it’s more expensive to compute (more complex pixel shaders), and only works on platforms that support depth textures. Furthermore, you have to use Deferred Shading or Legacy Deferred Lighting rendering path, or make the camera render depth textures from scripts.