Personally I’d prefer not to have someone speaking for me, despite the supposed anonymity of the accounts. If you post any amount of content, it’s likely the account can be linked back to you after the sale, which could prove problematic depending on what the new owner does with it.

But I’m a bit paranoid about such things after experiencing internet stalking. I don’t see anything morally wrong with it, just that consequences from the sale might affect me negatively in the future.