BuddyPress.org

This doesn’t sound like a BuddyPress issue.

It’s a WPMU issue; to be more specific, it’s a theme issue.

Do you want to show a link to comments or do you want to show actual comments?

There are number of ways to do this… theme hacking or adding a widget which displays the latest comments.

Adding a widget would be the simplest, but it depends on what you want to do.