@Byte@schratze It's incorrect grammar to begin with, and should never be said to anyone. It's what happens when programmers and others have no idea what that means and just assume this is a valid Anrede.
@Byte@navi I honestly don't understand how this could ever become so widespread. The programmers are doing malicious compliance, maybe on purpose, maybe because they don't understand anything. And the official guideline is bad, too.
@Byte@navi it's related to the Dutch wird mooi, meaning nice or beautiful. So you're just wishing people a good one. Good morning, good day, good evening. Could be anything