I've been making changes to this thread in a Structured Discussions page, and suddenly it won't admit any more edits or new comments. When I press "Publish changes" or "Reply", the edited comment fails to update, and a red-pink rectangle is shown at the top of the comment.
I've tried to update the page from a different browser, and it does the same. I also can't add new comments or threads at any other Structured Discussions pages, I get the same error.