Essentially, whenever an Away View Camera is active, the player's actual camera angle never changes, and moving around is always relative to the player's camera that you control, and not the Away View Camera that's being currently looked through. This is fine in Strafe and Standard, in which the invisible camera movement is entirely manual and very predictable. However, in Simple, this is not the case and the player's camera can wildly change on its own, disorientating the player and their controls whenever they're looking through an Away View Camera. This merge request fixes that by making Simple apply Old Analog's behavior and make the player's inputs always relative to the Away View Camera if one is active.
On a side note, if anyone can find a better way to implement this fix without needing these couple lines of code here:
if (controlstyle == CS_SIMPLE)
angle += ANGLE_90;...then please tell me. It's pretty hacky and I don't particularly like it.