Obviously Time Warp is exploiting!

Hm. I'm wondering how hard it would be to maybe just make a small, invisible sphere around a ship that the nebula particles could bounce away from in a wake. I'm not much of a coder, so I don't really know how much trouble it is to code a simple physics thing like that. Any thoughts on this from a coder?

Almost anything is possible to code. The only limitations are the amount of time / work needed to code it. Coding particles to disappear in a wake might take a lot of time and effort to code, and only be a small barely noticeable thing. Then again, JeffL has shown us in the (recent) past that he will do things just because "It looks pretty".

Edit: This is assuming the nebulae are generated via particles, and not just 3-D images of smokey stuff (in which case, this would probably be impossible).

We're using the Spark particle engine, and it does support things like that, but it makes each particle more expensive, so we'd only be able to use a small fraction of the number of particles if we wanted to give them complex physics like that. Good performance is the most important consideration, and if nebulas lag people, then people will just disable them, and then there would be no point.