This vaguely reminds me of Styledit, the included text editor from BeOS / Haiku. It supports basic text formatting - alignment, different fonts/sizes/colours -

This vaguely reminds me of Styledit, the included text editor from BeOS / Haiku. It supports basic text formatting - alignment, different fonts/sizes/colours - but these are stored as extended attributes in the file, while the "actual file" remains plain text.