I've noticed some users posts don't display quoting of other users posts properly. The bbs quote code seems to be written properly, but it doesn't display.
Those users can fix this:
1. Click on 'User Control Panel' at the top right of this page.
2. Go to Board Preferences>Edit Posting Defaults
3. Click 'Yes' next to Enable BBCode by default.
4. Click Submit.
You can also see whether you have the options on or off by looking below the message input box while you are typing a new post.
Hope this is helpful!