Originally posted by classicgriff:

in part due to the fact that it is trivial to write a texteditor (with ansi-graphics, for *nix-console and/or DOS) that handles multiple textfiles in less than about 250 lines of code (in either c or pascal).

I'm not sure what coding simplicity has to do with it? If you're going to define it restrictively, the Microsoft Design Guidelines seem like the most obvious candidate, not some API they may provide to make things simpler. 😉 But I should probably clarify that in MS Works 2.0 you could drag windows around, minimize them, etc. It wasn't just a flat application with a window list, although I would call that a form of MDI too. (Basically like a tabbed document interface without the tabs.) See a screenshot here. It's been many years, but I wouldn't be at all surprised if it followed the Microsoft MDI guidelines.

I don't know about Windows 2, but the MS Works 2.0 (for DOS) had MDI. 😉

Originally posted by classicgriff:

I noticed it employs userjs, is that even supported in O19?

Not those parts of Opera UserJS that make it superior to GreaseMonkey, no. So that script won't work on Opera 15+. For GM-compatible UserJS you could install e.g. TamperMonkey.