privacy – Is address reuse always bad?

a) In this scenario, where B does not spend from the address except to send to the exchange, and A already knows how much B is receiving in rent, there is no privacy benefit strictly between A and B of using a new address for each transaction before A and B. However, it would be easily noticeable on chain to a third party that one address receives payments regularly, even more so if A pays from the same address each time.

b) A, and everyone watching the chain will know the address and every transaction involving that address.

c) No information will be hidden with regards to A and B. To a third-party watching the chain, they would not be able to know that is the same person receiving the payment every month, like they would if the same address was reused.

d) Overall, this is less applicable when involving just sending to an exchange. The benefit of using different addresses occurs when B sends the bitcoin to a new person. If B has all their bitcoin on the same address, then they will expose their entire stack to anyone they want to pay, even if they are only sending a small amount. For example, you wouldn’t want someone to see your total bank account balance when sending them $20. The other benefit is not having activity that is indefinable by third parties. Making payments every month to the same address would be noticeable.