How does Emacs determine the major-mode assigned to a file based on file extension, e.g. .txt or .odt? If the filename has no extension, and I don't do anything to tell Emacs how to treat it, what does it get, fundamental-mode? If I then set text properties, e.g. bold or italic, for strings within the buffer, copy the buffer, and then paste it into, e.g., libreoffice, can it be expected to catch the italic and/or bold face properties set by Emacs? Better: if I write my file, with its text properties from Emacs, and read it into libreoffice, will it treat the file as I intend? Or, only if a filename suffix tells libreoffice what I'm giving it?
That's the point of the title question: if Emacs knows what kind of file it's getting, will it not be consistent with that in what it passes along to libreoffice, Adobe, or whoever?