I live in Paris, and although I do not drive I have the impression that most drivers here are extremely inconsiderate. As an example, there is a crossing which is constantly congested with buses and lorries stuck in the middle here. This is mainly because nobody respects the rules or priorities. When an officer comes in to control the traffic instead of the lights, it gets "magically" cleaned up and the circulation is fluid.

'We'll all just avoid making any mistakes' is a really unwise attitude anywhere, but particularly when driving a car.

You are actually providing an example that the Parisian way of doing things is not as benignly efficient as you suggested in your first post.

The fact that you can not change lane without forcing is a normal consequence of the increase of the traffic. I think the unwritten rule is that people should not turn on flashing lights too early before acting. The better communication of the intents and a fair level of trust that other drivers will understand it (and not try to block you) makes driving a lot easier (in Paris).

A bunch of highly nuanced rules like this seems very fragile. If you are driving in this manner, you have a responsibility to be alert for things breaking.

The facts show that whatever the parisians are doing is definitely the wrong way to do it, and should be changed.