Is looper mode (and sensitivity) due to hardware limitations of the current gen devices?
Or is it because the debounce (or other) settings are truly a user preference (and can you explain more about this)?
Or are button combinations (e.g., bank up by pressing two buttons) the reason to have looper mode?
It’s in the manual. Seems to be 100% for the combo buttons.
Having Looper mode on means you can’t use button combos but the reason for Looper mode is to eliminate any delay in the midi message sending. Typically this is important for controlling things like loop pedals where timing is super critical. The fact that button combos can’t be used when Looper mode is active is just a byproduct, not the reasoning for the feature.
If not using with a looper, I can’t really think of a reason to have it turned on.
Sensitivity would be just a preference. Not dealing with how midi is sent but how the button triggers the commands. I find the default to be fine but I know some on here like to turn the sensitivity down all the way down. I may be heavy footed 
Hope this helps.
Also to note: having a double press and a press action on the same button will cause a slight delay when sending the press action cause the MC6 will wait to see if it’s gonna be a double press or just the single.
Really? That’s surprising.
yes. that’s because we decided to decouple Press and Double Tap. We can still change in the future depending on feedback. If we do change it, that just means that any user who is using Press and Double Tap together will need to change it to Release and Double Tap.
yes Looper Mode is there because of dual button press functions. It’s impossible to press both buttons down exactly and hence there needs to be some allowance and hence the delay. Looper mode removes that delay, but that means dual button presses are not possible.
Yes, usually event systems split up handling of primitive events like press/release from aggregate events like click/tap/double click.
Perhaps a backwards compatible way to add this is to add a new event (e.g., push) that is not affected by sensitivity and leave press as it is.
It’s a subtle and confusing distinction, but less of a surprise to legacy users.
I assume this wouldn’t require more memory.