Then rjs3+foo will file into user.rjs3.foo
I tried that and added the "p" right (lam user.* anyone p)
Was that a typo? It should have been 'sam', not 'lam' to change the acl. Once you've changed the acl, use lam to show the permissions on user.rjs3.foo to make sure it was actually set. Then try another delivery.
There is one other thing that may or may not be an issue. Do you have a sieve script activated for your INBOX ?
-Pat