Honestly you are allowed to vote however you want on whatever you want. Anyone that says otherwise can go fuck themselves. Flagging is a different matter because it censors the post, but voting is entirely up to you.
I up vote my own comments all the time because I want them to appear near the top of the comment field, it's called the benefit of having SP. I could care less about the monetary reward it's all about making sure my opinion is seen and pushed to the top of the comments. It also ensures very few people can flag my comment out of being seen.
So in conclusion you have every right to up vote your own comments, and I think as long as what you are posting is truthful information you should up vote your own comment so other people see it and it cannot be censored.