While it would be ideal for both sender and recipient to set their own fees, forwarding nodes can charge appropriate fees for both parties. In response to a question about negative fees, Russell notes that this would be a strange idea and complicate routing. The channel initiator pays all onchain fees, which is simple but potentially gamable. Although there are more important factors than Lightning Network fees such as opening and closing fees, current alternatives are complex and potentially gamable, so simplicity was prioritized.