Back on topic, the actual problem here comes from a lack of understanding of ACM.
Front-quarter shots (and all shots forward of the 3/9 line) are important because they are a constant threat and need to be defended against in a merge situation. The threat of the shot is what keeps the merge neutral, all things being equal. By having to defend against such shots, it either prevents wide, unguarded lead-turns at the merge or it makes it a trade-off for such a turn, where big gains can be made but at a large risk.
By removing the threat of a front-quarter shot, you negatively impact tactics in two regards: you penalize those with good aim and you penalize those with heavier wing-loaded aircraft that have heavier armament. Additionally, you train and ingrain the bad habit of telegraphing your intentions prior to the merge.
The threat of a front-quarter shot coincidentally makes merges more complex and calculated; removing them makes them predictable and very game-able. Additionally, the skill of merges without shot risk doesn't translate well whatsoever to any other simulator environment.
Conversely, the benefits of the front-quarter shot aren't without drawbacks. Due to the high rate of closure, any shot taken means the attacking aircraft will be at a disadvantage if their shot does not connect after the aircraft pass, as they will have given up angular advantage. The front-quarter shot is also the easiest attack to defend against, because it offers the smallest aircraft profile and a known general vector for the bandit.
Put simply: if you can't avoid a HO, you're doing something majorly wrong.
Last but not least, and perhaps most ironic of all, is where the idea of not taking front-quarter shots came from. It came from AW if I remember correctly. The devs couldn't code an adequately-accurate hitbox on the front of enemy aircraft, so it became comically-easy to hit another enemy aircraft head-on as the hitbox was larger than the aircraft itself. The resulting fix was to reduce damage taken head-on/front-quarter by 90% IIRC, to discourage abuse of the oversized hitbox. This resulted in duels avoiding tactics that used the HO because you lost angles and time in trade for virtually no given damage.
This came over to AH when pilots migrated from one sim to the other and the habit remained.
The disdain of front-quarter shots has nothing to do whatsoever with skill or ACM, it came from a coding limitation of another game. It's literally the gamiest aspect of dueling that has nothing to do with actual tactics.
The disdain shown by certain posters in this thread for high-angle deflection shots highlight the same lack of awareness as outlined above. Every deflection shot taken is a tradeoff for time and angles. If a defending pilot cannot make use of such counter-tactics, then it's due to a deficiency in the defenders tactics.
