As of this morning, I cannot see past comments or make new comments.
The Trello cardback design has changed to fit the more modern Trello visual appearance. This addresses one of the common complaints about comments being so far down the card, people have to endlessly scroll. They are now on the right side of the cardback:
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.