Operating system: Both Windows and Linux
Graphics card: Various nVidia cards
Worked: (newest version of Blender that worked as expected)
Create an object with two separate components. Set its origin to somewhere strictly between the two components, so that the origin is not part of any face. Generate particles on that object. Then a particle can appear at the origin.
Exact steps for others to reproduce the error
Create two planes. Space them apart. Join them. Set the joined object's origin to geometry. Put a particle system on it. Change end time to 1. Observe a particle is generated at the object's origin even though there is no face there.