What are you talking about?! Cripes! I believe I only got the first period... Could you explain it to me like I was a two year old?...
Quake had lots of optional graphics setting. One was a custom FOV (like AH), that you could expand to see pretty much all around you. The edges of the screen would be behind you, the center was a compressed view in front of you.
Another one was to turn mip-map settings to only use the smallest mips. It's like the anti-hi-res texture pack: you're using say 16x16 textures instead of 1024x1024 textures. Turn off filtering, and what you get is a world view that is big giant blocks of color. If you knew the map and what to look for, you could easily navigate anyway.
The FOV change meant you could see all around you, the mip change had the dual effect of greatly increasing framerate (software renderers back then) while also making enemies and weapons stand out against that background. The guys that got good at navigating in this environment had a huge advantage.
Dawger is suggesting the same thing: by turning down graphic detail on the terrain, you get a washed out terrain that small objects will show much better against since they can't hide in the detail, and since those small objects are generally airplanes, you get around the no icons setting and any skin scheme chosen by your opponent. Basically turn down graphic detail and make the game look worse in order to gain a competitive edge.
If that's not clear, maybe later I'll get some time for some screenshots. A quick web search didn't turn up screenshots of those old Quake days.