Re: How do you do this ?
@Boone Gorges : great, thank you !
This should be documented somewhere in the BP doc
i only found this:
bp_dtheme_blog_comments( $comment, $args, $depth ) X-Ref
Template for comments and pingbacks.
To override this walker in a child theme without modifying the comments template
simply create your own bp_dtheme_blog_comments(), and that function will be used instead.
Used as a callback by wp_list_comments() for displaying the comments.
param: mixed $comment Comment record from database
param: array $args Arguments from wp_list_comments() call
param: int $depth Comment nesting level
This tells we can do something not how we can do that. You give the right answer 
