So you are saying that Atlantis is an old reader, since it can't understand \u256?In this way, old readers will ignore the \uN keyword and pick up the ANSI representation properly.
Change the example to \u474 and now even wordpad uses the \u notation. Of course these are followed by ?, so the old readers can put in a question mark for things they don't understand.
With \u474, Polyedit, OpenOffice, Abiword, Wordpad and Copywriter can all open each others files. Now, Atlantis can open none (and display the proper character), and can't make its own file, unless of course \u474 is in some ANSI page.
I don't really think there is any disagreement here, Atlantis is an old reader, at least according to Microsoft.
The point for me is, when I want to put in a character from some unknown (to me) language, I will go use BabelPad (or Character Map) and paste it in from the clipboard. Not possible with Atlantis since it doesn't understand the \u notation. Much simpler than trying to find the correct ANSI page.