I would have to know which page template to give you an answer. I am fairly new to BuddyPress, but I am pretty familiar with php and html, so I can usually find things. If you can explain a little bit more of what you would like to do, perhaps I could help you out.
I was able to resolve this for anyone with the same question. The code to change is in the buddypress/bp-themes/bp-default/functions.php file around line 644 `’title_reply’ => __( ‘Leave a Reply’, ‘buddypress’ )`
