This should not be cheat protected.
I used to play on a crappy PC, and needed low quality settings to run Trem smoothly. For some reason, with low quality I couldn't see at all in some areas (the example I remember the most is the window room in niveus, up in the ceiling it was pitch black.)
Now I play on high quality all the time, and I can see anywhere just fine, but for the players with crappy comps, I say leave it available.
As for seeker's pic: the gamma in the first half of that .gif is a lot lower than what I play with, and there's no way a dretch could hide there unnoticed with my (r_lightmap 0) settings.
When I was recording demos they turned out dark. I tried setting r_gamma higher but I believe it is capped at 3. Like I said I have no problems with visibility now, and I've never been a user of lightmap so I'd just like to represent at least one person who doesn't use it, but thinks it is okay to use it.
There may be few similarities between this and binds, but this is a purely visual aid. In fact, it reminds me alot of the alien crosshair debate we all had not so long ago. That too, is a purely visual, yet non-standard aid in gameplay.
Tl;dr version: I'm not going to hide in a place that isn't covered by a wall or some other obstacle, are you guys? If so: you're retarded. If not: this "cheat" really doesn't hurt you at all, so try not to be upset about what others may gain from it.