I still would just edit and add their name in, doesn't concern me much if they get the notification, I'm quite sure that if they had something constructive to add, they would be interested to hear the response, and check the topic the next time they visit the board.
It's just common forum etiquette not to post 3 times in a row - ever. Unless you mean to bump a topic, or where the time gap is around 24 hours. I don't think Scirra's Replies should bother this at all.