Just double checked – index.php is in the same folder location in my child theme. Dumped the cache, no change. I’ve just added arbitary text inside both the content and padder divs, to check if the changes were rendering, which they are not.
That said, there’s a h3 tag [h3][?php _e( ‘Site Activity’, ‘buddypress’ ); ?][/h3] that isn’t rendering either…
Strange thing is I’ve been able to edit /activity/entry.php with no problems.