I have the same problem as the OP.
I can make a reply to another comment. But I can't find a way to create a new comment.
I also wonder if it's the same login as for the forum; if you try to register to leave a comment on the news item page using your usual GTP username, it tells you that the name is already in use, and if you log in you are taken to your normal GTP account page.
Any hints?
DJ
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