In most cases control column movements do not tell you what the “other guy” is doing, only what he has already done
... but it tells you a lot on what he is trying to achieve regarding airplane attitude
and it is already a lot compared to his sidestick which tells you ... nothing !
Monitoring of aircraft performance either from instruments or visual cues, or a combination of both, tells a pilot what is happening to the flight path, and therefore what the other pilot is doing.
You are right for 99% of the situations
but I strongly disagree for the remaining percent, when weather conditions mix and mess up with your inputs
I do not share either your view on "summed" stick inputs.
If a guy has to intervene, even in the most discret way, RED BUTTON must be the only way to go.
Otherwise how would you rate your action versus his, and how would he rate his action versus yours in the resulting attitude change ?
I do not think Airbus would recommend such interference.
At least have not seen anything like this in the FTCM.
You make a good point with the "Taking over" situation.
Saying so, we do not expect fighting on a flight deck.
Nevertheless, your anecdote emphasizes the point I wanna bring:
If a guy does the same with a sidestick, you will not notice his action on that sidestick, but only the result of that action: Nose pitch up
So, already, you are a little behind in your assessment of the situation, and in your intervention.
I believe you could have been much closer to tailstrike with sidestick philosophy than with your control column.