To be honest, I'm not. Even on reddit (yes, I still like reddit, it has some cool stuff) I post pretty freely. I don't post about sensitive issues, but if someone who knows me looks at the comments I make, they could easily find out it's me. Frankly, it's not too important to me if someone knows who I am, since the subjects I talk about are those I talk about irl, and if I wanted to post while remaining anonymous, I would. As long as you're careful with what you post, I think it's ok. Also, on the karma system, I'm going to go against hubski popular opinion and say that it's not too bad after all, as long as it's only reddit and its clones. It leads to a rise in popular opinion, so you can study what most people of a certain demographic think, like, and hate.