I've been getting this comment quite a bit, and it confuses the hell out of me. Never in my life, with the thousands of games I've played, a large number of them being top-down shooters, have I encountered the controls you are describing. A major inspiration for this game is the web based shooter RoboKill, which has identical controls. Maybe I've been in a cave my entire life, but what you're saying to do sounds like the most backwards and unintuitive system I've ever heard of.
I understand he has since changed but +1 for Mark's original position. In my opinion too, current movement system is confusing and it should be a simple WASD - each key making the character move towards the direction these keys generally do, regardless of player-character orientation.
I haven't played RoboKill you speak of and *probably* most your players also won't know about it.
What's for sure is they won't read your forum post above and change their opinion, as Mark did.
I'm trying to learn C++ and develop a basic pong as I go, seeing the effort goes into my tiny project, I can only imagine how much effort goes into a proper project like this. It would be a real waste if your game gets closed by interested players after them getting confused for n seconds. I suggest you reconsider your "defence" on how current system is great and the suggestion many people made is "backward and counter-intuitive". In my opinion your current system is counter-intuitive. I only tried the web version, if you do not have it yet, consider adding keybindings option to your game so that at least the semi patient players can *fix* the keys and enjoy the game.
Good luck with the project.