How does the rating system in HN works ?

You're doing just fine, the voting system is on the blink, Paul Graham (the owner of this site) is working on it see here:

http://news.ycombinator.com/item?id=871202

In short, your votes are registered, but are not always counted towards the credits of the thing you have voted on.

It sounds like there might be a waiting period before voting is counted. It could be karma or time based, but honestly either it way it is probably a good idea to slow down the spammers.

Try commenting and participating for a couple weeks and I bet it will start working for you.

I think PG said something about he is experimenting something with the ranking system.