Louise, the email you have been sent is legitimate.  You get these message when someone else has replied to a comment you have made on the message board, even if the reply is days, weeks, months, or even years after you posted your comment.  This actually happens pretty often when people post new information on companies that have been mentioned as slow or no-payers in the past.  In this case, you received a reply to a comment you had made in 2009 here.

(You probably got another reply notice when I posted this comment.)