BuddyPress.org

We have to try to get things to work for 80% of our users; if we encouraged people to edit the default theme or any of the core BuddyPress files directly, most of those people are going to come back and complain when we release a new version of BuddyPress because they won’t understand what’s really happened.

Theme developers of course have two options — either as a child theme, of BuddyPress’ bp-default or one of the many other theme frameworks, or as a seperate/existing theme with the BuddyPress template files copied in. Both have their disadvantages and advantages.