The merit button will be visible only if the person has atleast one sMerit to send that is why OP not aware of that sending merit.
This is not true, as far as I can remember, I have seen merit option when I didn't have smerit and when I was a newbie.
First thank you ognasty for giving me 2 merits. And yes it's true what mersal said. I did not saw merit option before but now I see it. Well thank you all for valuable response..