[quote]Why didn't Bungie let the people who [i]could[/i] change their namplates know, before their nameplates would never be able to be changed?[/quote]They did. They gave literally months of notice.

[i]How[/i] did they give notice?

By posting updates on their website- and on the front page of the website- giving you around 3-4 months of notice. It is your own fault if you did not check the official website for official news.