This question is proposed to all of us. So far no specifications have ever been made either by TG or by DKF. No restrictions are placed on the use of auto fire, multiple buttons mapped for the same purpose on keyboard. As far as I know the concave and convex issue has never disqualified a score. Even if you only had the concave buttons, there is different positions to set the jump as well such as requiring it to be pushed 2/3 of the way down before input clicks, 1/2 of the way, or 1/3 of the way. No one really concerns themselves with these issues. Besides, how would I even verify the keyboard mapping, auto fire, etc? People can say and do what they want in this regard as far as I am concerned.
But... I will say this... if you are playing on cab it would be a players choice to consider factory settings. If the buttons are concave then use concave, if the button input position is 1/2 push position then have it set to 1/2 push position. I think this is important for the player to place them self with others in this regard. It is not just an issue of getting a high score but did you do it in the same way with a level playing field as others. I know of someone on the DKF HSL that used a MsPacman joystick on their cab with no restrictor plate. No one has fussed about it.
Mame is another animal. Since there is no default mame mapping for DK or DK Jr then maybe consider making it as much like arcade with one button for jump, and no auto fire. But like I said, no one can verify keyboard mapping.
I don't think we need any official rule accept maybe to mention what is allowed so that this question can be anticipated and be already answered for newer members or anyone else for that matter.
Thank you to any and all who chime in on the question.