@hnla – While your method is well-intentioned, it breaks actual 404 pages. Try typing in example.com/hfklsadjfkasdhf and you’ll see the activity page, instead of the 404 page!
You could just copy my code directly into the bp-default theme’s functions.php so it will be overwritten when the next version of BP comes out.
FYI, the code can also go in wp-content/plugins/bp-custom.php as well and not necessarily in a child theme’s functions.php file.
