BuddyPress.org

The problem is that the src path is relative. On your blog, the path is relative to the correct place. Once the item has been republished, the reference is no longer valid.

I suppose you could write a filter for bp_activity_content that would detect this kind of code, call up the correct URL of the blog, and rewrite the src path as an absolute path. Not sure how consistent it would be across different blogs, though.