Doomsday Engine

In practice this would require the particle logic to make hit tests against mobjs, which may be difficult to pull off performance-wise.

I personally think this should be ignored because it would result in dependencies between the playsim and graphics systems that would be very difficult to integrate with the gameside playsim logic. Also, given the need to vary the number of particles in a view-dependent way this would logically demand that a particle which can be collided with must still be spawned. Not to mention that in a network game we'd either have to communicate the collision outcome on client side back to the server or perform particle collision detection on server side.

In short I think this is not the right approach. If the player should be damaged by a particle generator then the existing mobj mechanism must be used in order to integrate it in a multiplayer game. Thus, there is no benefit to this feature (simply spawn both particles and "damaging but invisible mobjs").