Sometimes we change your display name on the forum if you send us private messages just to ensure it gets to the right person.
If people have the same display name on the forum, one that registered 2 years ago, and maybe someone that registered a few weeks ago, and we send a reply to the user that registered just a few weeks ago, our message would end up in the wrong user's inbox since the message would go to the user who first registered on this forum and used that display name. There could be 50+ "Amy" users on the forum for example, and only the one that registered first of these users would get the pm sent to any amy.
So instead of having users coming back being angry or annoyed that they never got a reply to their question or message, or in general spending time on writing replies that never end up getting read, I myself and I believe other admins too modify the display name first before replying to ensure they do get their reply. Of course this is only done to newer registered users that might not have been seen around that much, not having set up much on their profile or similar.
So there's not really any hacking involved, nor any glitch at play, it's just a thing an admin might do to ensure their message goes through. You'd be surprised how much typing that has gone out into thin air due to users using display names already used by others. Of course sometimes there might not be another user with the same display name, but "Anca" is a rather short display name and the game has been around for some time so it's usually better to be on the safe side. If I'm not mistaken I'm probably the one who modified your display name after you contacted me here.
Hope this explains your situation, and you can easily set back your username to whatever you please, but it's always good to double check PM actually works for it and people can reply to your messages.