Jesus, this is an impolite thing to say, but believe me that when I was making the Positivity Thread, I was already thinking "Lumifer will probably be the first one to object against this, and I just hope he won't do it directly in the thread". So, thank you for not doing it directly in the thread.

You know, even in this moment I am not really sure whether you actually have no idea what "nice" means (I assume that just like some people are colorblind, others could be nice-blind), or whether this is just your style of communication. As a consequence I am not sure if trying to explain something to you gives me a chance to be somehow helpful, or whether it means you have successfully made me your plaything (because I have no doubts that whatever I write here, you will be able to find something to attack). I am not interesting in playing verbal games online, and when I suspect someone being too fond of such games, I generally try to reduce my contact with them.

One of the problems with "when I see a weakness, I must attack immediately" style of communication is that is makes it impossible to discuss issues which we cannot sufficiently exactly express yet, such as pretty much anything about human psychology. Then the issues must be left uncommunicated.

Is niceness just politeness

As I understand it, both serve a similar goal -- both are strategies to reduce conflicts between people, and make cooperation easier. But they are different strategies, based on different approach. Politeness makes people easy to replace; niceness contributes to long-term personal relationships.

Politeness tries to achieve its goal by reducing personal involvement. The ultimate form of politeness would be a person strictly following the rules of polite behavior and doing nothing else; like a robot with no personality behind it. Different ultimately-polite people would be perfectly replaceably by each other; if you wouldn't see their face, you would probably notice no difference.

The idea is that you could still have a conflict with such people about "you want something, they want something else", but all other sources of conflict would be removed. This is a required skill for a diplomat; and there is a stereotype that Japanese people behave like this.

Niceness assumes that you care about the other person, as a person (not merely as a tool to reach some business agreement). Nice behavior leads to the kind of long-term cooperation where the individuals are not replaceable. The cooperation can grow beyond the context where it started.

Politeness is a good choice when having to deal with many strangers. Niceness is a good choice when trying to build a community.