I'm confused as to why this is really a big problem. Sometimes, people really muck up replying inline, and it is somewhat harder to find their comments, vs. having their comments completely seperated from the previous message. Perhaps it depends on the class of user that you are serving, as well.
The author seems to think they want to have a conversation with him. They don't. They essentially have sent him a form to fill out, and they want the answers together at the top because the answers are all they care about.
That's because you're not having a conversation, you're filling in fields in a form. You're lucky they let you use email instead of redirecting you to a web form that more rigidly enforces the method of interaction with them (which needs to die even more).