Based on your description, I think that would OK. I’m assuming the generated email address would send a private message from Discourse to the original sender.
Our email users simply assume that replies from their email client will go to the sender not the topic, because that’s how most Mailman lists have worked for years. It would be nice to offer them a way to add to the topic through a mailto link in the message, but this isn’t a requirement for us.
Having Reply All go back to the topic is a problem that may very well be unique to us. My users have learned that Reply doesn’t include everyone on other emails, so they always hit Reply All. Many of these users see the CC field as just another place to enter email addresses. They don’t really understand the difference between TO and CC.