Well, what is stopping the users from posting after they've read the thread and if they liked it use the code?
because it would still be in your post and not the post the user added rep to, unless you had some way of adding the users name in also.
When I made this I had the idea to use it to speak to the original poster, mostly used for thread creators and you like their thread.
But as the code is in your post the thread starter may not know its aimed at them unless you could add something in.
You can easily just say "Thanks NAME for this post", and/or "Thanks for this great thread!" if their not stupid they'll catch on.