When someone makes a reply on the board to a post you have made it also comes to you as an email. It’s designated in the address that it comes from the Fool system and says “Visit Topic or reply to this email to respond.”
This is an alert that this is not an ordinary email to you. The person didn’t send an email to you. He or she posted a reply to you on the thread. If you reply in an email to the person your reply also gets posted on the thread. It’s not a private email response!
A board member who engaged in a several post back and forth discussion thinking it was all off board was surprised to discover that it all was in the thread. He/she was glad he/she hadn’t put anything personal in what he/she thought was a private email exchange, and thought I should alert you.