Hi guys,
Yes, like Jim and DerStrom pointed out the initial post is usually a question so it's not enabled for it. I do understand that there are first posts that are not questions hence the rep button is still there.
The +/- system is complete and fully functional. If there is any reply in the thread that you think is useful vote for it - even if you haven't made a reply in that thread. If you vote for it, it not only gives that person rep points but also shows any other readers that the post is somewhat valuable.
Regards,
EM