You are right. I'm still new in this site and don't know how to upvote comments ...

alter8 · on Sept 13, 2012

I couldn't get this joke. What is this supposed to mean?

aortega · on Sept 15, 2012

It was no joke. How I upvote something here?

alter8 · on Sept 15, 2012

Click the arrow that is to the left of the commenter's name. It seems you are one of today's lucky 10,000: http://xkcd.com/1053/

I made a bad assumption because your account is almost one year old. I'm sorry. Now I see that information is not given anywhere in this site. I think this vote method was taken from Reddit.