After spending some time this morning running through the issues discussed in this thread, I've essentially been able to confirm everything outlined.
- Right now, unless you are running MSAA or TXAA under DX11, the MWO client is forcing PostAA 'On' when dropping into a match or the Testing Grounds, even if you confirm the r_postaa=0 entry in the systemoverride.cfg and that Anti-Aliasing is set to 'Off' in the MWO client video settings.
- Manually switching the Anti-Aliasing setting to PostAA in the video settings, saving, then setting AA back to Off and saving, removes the forced PostAA in the Testing Grounds only. This workaround only applies as a real-time change in the Testing Grounds; it will (likely) not work after dropping into a match.
- The forced PostAA condition re-establishes itself with each new match and Testing Ground session, so resetting it between drops will again not resolve the problem.
- The 'halo' artifacts are a somewhat separate issue, produced when implementing higher quality levels of the Post-Processing setting in combination with PostAA.
I don't have an ETA on a fix yet, but our QA team is aware of this problem and the issue is of high priority. I will be keeping this thread updated as regularly as I can as new information becomes available.
Until we can roll out the fix, I recommend that everyone who is unable to efficiently run either MSAA or TXAA turn their Post Processing setting to Low. This will at least help alleviate the halo issue, and somewhat reduce the intensity of the ghosting.