Dear omkar,
Regarding karmas, you can see good post and not so good post below it. Once you click on good post, your karma will be increased by one and once you click on not so good post, it will be decreased. This feature is only to encourage all the devotees for nice topics or it is a kind of gesture to appreciate when you read a nice post. About your username, only the admin can do that. Will notify him. Baba bless you.
om sai ram.