Comment on tweets?

Hi. I'm new to Twitter and I got a problem. When I find a tweet I wan't to reply to, my comment is not going to be under the tweet... Why not? This is in the iPhone app. I can see that other people have made comments under the tweet but I can't...

Can someone help me?

 

Not happening on my twitter?

If you look at this tweet https://twitter.com/MrBuchwald/status/347802645647462401 I know of at least 3 people beside myself who made a comment on that but it don't show the comments under the tweet neither on my iPhone or my iMac in Safari. It just goes on my stream as a normal tweet saying "in response to" but not the tweet itself so people has to either guess or find it themselves.

??