In CR#315342, you may disable the 'Fn-shift' by not assigning any modifier key to KEY_RESERVED.
I'm not sure if you mean the separate keydown and keyup events sent by the virtual 'chording' behavior. @tdm carefully designed this so the events are sent in a 'safe' order (i.e. shift down, key down; key up, shift up). The current keyboard driver does not repeat keydown events if you hold the key down.
The way I normally check the event stream sent by the driver is with 'adb shell getevent'. The output of getevent has three values, the event type (always 0001 for EV_KEY), the keycode