That's a valid and valuable point.

Personally, I don’t want people to write just what other want to read.

Instead, I want people to write what they really want to say without thinking about their score

In a way, both systems are just different implementations of social regulation. One system achieves it through numbers. If you remove numbers, people will still express their approval or dismissal, in words. This has some regulating effect on what people write, how openly they express themselves. And I'm not even sure that's a bad thing.

Of course, in a system with karma people can still additionally express their reactions with words.

My main point is, we cannot have a system without social regulation, that's just an inherent part of human interactions. I can think of reasons for and against amplifying it further with karma. Personally I like it though.