I thought about this case in the not-so-recent-past and came up with the possibility of creating a "submention" similar to the idea of a subtweet. If you scroll down on that particular post, you'll see a response from Colin Walker about actually implementing it, which he implemented as a nomention plugin for WordPress.

Of course doing things this way doesn't necessarily prevent the person from possibly seeing it through the natural course of events, others notifying them directly, or even the use of things like refbacks, which would send them notifications anyway. And then there's Voldemorting...