1) Yes, and it's not necessarily bad practice - it's a common and recommended thing to do in many cases. Sometimes, because a role controls a domain or works in a general area, others need to count on it for something so that they can get their purpose met, and that's just fine. On the other hand, it is often bad practice to stick extra accountabilities on a role that don't serve its purpose and that don't naturally fit that pattern.
2) Yes, it's allowed, and often quite natural - just because another role controls the domain doesn't mean you can't just ask them for permission or propose some accountability on them to get your own accountability met. Can you raise a valid objection to it on the grounds you've cited? Maybe, or maybe not - depends on whether you can answer the objection test questions and validate the objection...
Hope that helps!