For some reason I only get that on some servers. It doesn't look exactly the same (because my config is different), but the texture in those cases just looks different from the usual. I still haven't figured out any logic behind this, but then again I really haven't even tried.
Gammabug. I think you get that when you change r_gamma, don't vid_restart, change map, change r_gamma and vid_restart. I could be wrong with the details, though, there's a tutorial somewhere on this site.
Preventive measures has been taken, it's impossible to use that technique nowadays. What I am experiencing with my configuration is something similar, not that obvious, but they really light up, and makes it very easy to spot them.
it's a vid_restart bug, i dont remember how to do it but i do it by accident a lot. theres a guide on here written by someone about how to do it. makes the game look like shit
when your gamma is at 3 with ignorehwgamma at 1
you put gamma lower (for example at 2)
without vid_restart then on the next loading stuff (changing map) this bug will happen