This bug happens on my iPhone too, in Safari, with Desktop mode enabled. It happens both in wifi from my router, and 3G, with wifi turned off on phone.
I asked some friends to try to emulate this; no word back yet. These are the steps I gave them.
- Go to this link.
 - Scroll to the first comment, by user emo_pinata.
 - Click on the Replies button (it should say 6 Replies).
 - Count how many replies there are. (I’m getting four.)
 - Scroll down to the second comment, by user atl.
 - Click on the Replies button (it should say 1 Reply).
 - Does the reply show up? (It doesn’t for me.)
 - Go back to the first comment. Click on the Replies button twice. Scroll down a little then up.
 - Count how many replies there are. Are they all the same (from user KXKVI)?