Obviously some captains (who think they know better than the manuals) think this is their "right".
They have every right to cover the controls at critical stages of flight, but then every PNF should do this. They shouldn't make dual inputs unless they have stated they have control and you have responded.
I would without doubt bring this up with the captain(s) in question. They may have a reason for making inputs and it is their right to take control at any time. The safety implications of dual inputs in the flare and at any time in flight have been covered by BOAC and others already in the thread. I wouldn't "quietly put up with it". If they are making dual inputs without taking control it is a safety problem and you should deal with the issue positively, firstly with a cordial and polite conversation with the skipper.
As an aside it can be frustrating to fly with a Captain who perhaps lacks confidence in you as a co-pilot and acts in a way that you perceive limits your ability to think and fly in the manner you are accustomed to. These guys exist in every airline. I have found the closer you get to the LHS, the more you put yourself in their position, and it gets easier to understand why some skippers act in this way. It is not a slur on your character or ability. Ultimately it is their command and their responsibility, and is just part and parcel of life as an F/O. We all get the chance to move across to the LHS eventually.