Confluence 4.1.9:

It can easily be seen that the comments are currently collapsed because:

1. there's an arrow pointing in the conventional way to depict collapsed content, and
2. the "7 Comments" text is in the same colour as other links, so it shows it can be clicked.

Confluence 5.0.2:

It looks like we're seeing buggy behaviour because Confluence claims there are 7 comments, but it's not displaying any of them. There's no indication that clicking "7 Comments" will do anything until you hover your mouse over it and your cursor changes to a hand.