Re: Replace Activity Stream blog excerpt with the_excerpt
Isn’t it possible to grab the excerpt based on &$post?
$post->post_excerpt.
Sample code:
http://pastebin.com/s9PajKjU
Disclaimer: Untested 
[EDIT]
I see what you guys are talking about now with bp_create_excerpt()!
You can either request an additional parameter for unfiltered text in the “bp_blogs_record_activity_content” filter or in the “bp_create_excerpt” filter.
Definitely a good idea for a patch!
