What is kindness ?

The quality of being friendly, generous, and considerate.

Note the words in their exact meanings:
friendly is not the same thing as being a friend,
generous means not expecting a return, giving freely, possibly sometimes giving more than one can afford (see the parable of the poor woman who gives all she has),
considerate means taking care to consider the needs and preferences of others.

There is the implication that kindness has the quality of being impersonal,
it is often granted to strangers.

In my view, it's catching. Have you ever noticed how if someone does something nice for you, it lifts your heart for the day and makes you feel more inclined to be nice to others?

Some people here are very kind.
A few are borderline - perilously close to being trolls.
The best way for a social site to degrade is to allow trolls to get away with their destructive and toxic nonsense.
If you come across anyone being abusive or harassing you in any way, don't hesitate to flag (report) them.

People have their moments here, not always though.

For some, no. People don't get friendly when you're friendly, especially if you didn't do anything wrong.

Caring about how other people feel.

im kind to people i dont hate

Some more than others

everyone is kind once in a while.