Erichos, I have to disagree with your analysis of the diode problem. I'm a proponent of diode-less single row matrices, but if you have two buttons pressed in a row, it can trigger a button in the row more distant - ghosting. The three button press problem is masking and it will occur in the column farther from the three buttons pressed, in the far row. Electricity will follow the shortest path.

If you leave the diodes out on a two or more row matrix, sooner or later, you're going to get weirdness. It might not manifest all the time, but in a world where an extra AMRAM means the difference between life and death, I'll put the diodes in. The worse case in my mind is you have a store release or staging action where not commanded. The masking issue is probably less severe in games as you might actively remember the masking issue and let up on buttons.

Diodes are cheap and they allow an immediate expansion capability to new rows. If you have a fixed form joystick like a TQS that you can wire up single row, fine. If you're making a frankenstick or a button-box, put the diodes in if there is any chance you will ever add that second row, just to save yourself the time and annoyance of soldering to already placed switches.

You're right that if you're commanding single buttons only, you won't see the problem. When I'm cranking, banking and popping flares, I don't want to see my goal popping payload go flying away into the dirt and I have to RTB just to re-arm.