It's pretty lame to up vote your own comment.
There, I said it, I think it's really lame that some users force themselves to the top of every comment page by upvoting themselves. I would like to see how the community feels first and if they choose to vote your post to the top, then it's fair game.
In my opinion, we should disable the ability to up vote our own comments.
If it was not allowed a user would simply use aliases to upvote their own comment, making the system more dishonest.
Is it like being that guy who likes his own posts on facebook?