PLEASE READ THIS TO CLEAR UP YOUR MISCONCEPTIONS OF WHAT QUICK SCOPING ACTUALLY IS 
Scoping: Right click, increased accuracy, see further.
Quick scoping: Zooming and shooting immediately (zoom animations will be drawn every time), assuming that you will hit what you were aiming at unscoped. Almost all games, except for QW, allow this as you are essentially right clicking+left clicking, and most of the time they auto-unzoom for you. MISCONCEPTION- You are skipping the zoom animation or you fire faster. FACT- What you are doing is really zooming normally, except instead of taking the time in lining up your shot, you are risking that you will hit what you were previously aiming at.
Quick scoping in QW: Same as above, except for the lack of an auto-unzoom feature. This is where the the right click, left click + right click comes into play. MISCONCEPTION- You are skipping the zoom animations and firing faster. FACT- You are manually unzooming instead of staying scoped for another shot. What this does is prevent you from experiencing the wait period between firing shots scoped so that you can either run away or switch weapons.
So if you consider this an exploit, I want you to ask yourself something. If someone were to zoom+shoot without adding in the manual unzoom step required in QW, will that prevent them from killing you? You know that in order to zoom+shoot as fast as possible, the zoom animations must be drawn first. Go into a server and try it yourself. Then think about the quick unzoom that is standard in most games, which tend to insta kill no matter where you aim. If it doesn’t increase the time it takes to fire your next shot, and simply works around the awkward assumption that you are going to keep shooting scoped, then how is this bad? This allows you to use the sniper rifle in two ways. Distanced- always scoped / Close Quarters- 1 shot, with a possible swap to pistol if you don’t hit head.
If you think the zoom+shoot is an exploit, that is the normal zoom in system with the minimum allowed time to fire a shot after the animations are drawn.
If you think the zoom+shoot insta kills, it does the exact damage as if you were zoomed at any time and only kills if aimed at the head.
If you think the zoom+shoot+unzoom allows for a faster RoF, increase in damage, higher accuracy, you are both right and wrong in a few ways. The RoF does not change as you are scope, shoot, unscope, wait, scope, shoot, unscope as opposed to scope, shoot, wait, shoot. The damage and accuracy are the same as being scoped, as yes you are scoped in this case aren’t you?
This is basically as clear as I can make the case of “quickscoping in QW”. It does not exploit anything as far as I can see. It still requires you to aim regardless of what you are doing with your mouse. It doesn’t create any imbalance, and only makes the sniper rifle an actually usable weapon in close quarters. I am going to go out on a limb here and bet you that even guys at SD would consider this perfectly fine as is. The lack of knowledge is where it becomes an issue with people, who somehow think that quickscoping makes bad players good. If they kill you, they aimed at you. If they unzoom immediately instead of setting up a second consecutive shot and kill you, your still dead. In the end it is completely dependent on aim and movement. No matter how you cut it, it is a very sensible technique that is in no way exploiting the game.
I’m not blaming you, and it’s kind of hard to blame SD for poor implementation… it is what it is, some will agree with it, some won’t… i won’t.