This thread is becoming really interesting.
Ray, here's an example of reflection acting as diffuse flux source over the field of view. In this case it's a cryogenic camera, binned and running at photon counting levels (16 bits) but using a single integration instead of amplification/scintillation counting. Turns out you can photon count with integrating cameras if the optical efficiency of the entire system is above a certain threshold. For example, we ran the CCD at -110'C, the lens had an f of about 0.9, and it's a TBI CCD with about 70% QE at the emission wavelength.
Anyway, note that the bright targets illuminate the areas around them, even though they are contained in black wells. Further, the targets sum to illuminate the entire black well plate. This occurs because light reflects from the rear element of the CCD (very close to the targets). The reflection is sufficient to set a bottom limit on sensitivity.
These are rather special conditions, and you are probably correct that the IQ is showing xtlk. I think the second picture supports your view. Here I just snapped a monitor in a dim room, IQ180, LS150, f4, 2 sec, iso800. Note the repeat of the saturated monitor light at the left - and the black stripy junk. I have seen the black stripes before, but the xtlk not so much because I rarely boost exposure. Here I boosted exposure .7, ran up shadow to 25 and bumped the contrast. Spot is only a half dozen gray levels and difficult to see otherwise.
Matt, my head is buzzing.