You may think that intuitively people want to subscribe to topics they reply to, but our experience shows us that very few people want to make use of subscriptions. Currently, only 2.5% of the forum members have any subscriptions. Many people (myself included) don't want their inbox cluttered with forum posts and replies.

Making the "subscribe to topic" default to checked for replies would clearly not be what the overwhelming majority of members would want.

Bruce Luckcuck
Director, Applications & Support Services
Wiley Publishing, Inc.