One example of a mitigation for this kind of behavior might be to allow users to ignore messages for accounts younger than X, where X is a length of time chosen

One example of a mitigation for this kind of behavior might be to allow users to ignore messages for accounts younger than X, where X is a length of time chosen by the recipient. This is only a mitigation, and there are plenty of ways one could get around this kind of limit. However, some action would be appreciated.