誰が返信したか表示されていない

For example, the 28th post and 30th post both reply to @Stephen 's post(not the same one). But only 28th post display "reply to @Stephen " sign. So I copied the post without the sign, deleted it and reply again, then everything go right.

We have noticed the same thing on our installation. It appears to be normal behavior, when a user replies to the immediately preceding post.

This post should teach you more about it: