BuddyPress.org

@fortinmichel – The patch allows you to override the auto-generated excerpt. You still need to actually write the code to override it.

I already answered this question. Answer is available on the first page:
https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/replace-activity-stream-blog-excerpt-with-the_excerpt/#post-67290