[poizan42]

> FWIW, old Office documents were actually CFBF (Compound File Binary Format) files

That's actually the "new" binary formats. The usage of CFBF seems to have been introduced in Office 4.2 (at least Excel 5.0 is the first Excel version to use them, it's hard to find information about the old Word document file formats).

> The side effect of all this, however, is that the data inside an old Office file is not laid out in a logical way - streams consist of non-sequential interleaved blocks in a seemingly random order (depending on what was written when), some blocks may contain garbage data, and so on. So it's very difficult to reverse engineer, which is why it took so long back in the day, and the results were often unreliable.

I don't believe the OLE compound file format has ever been much of an effort to reverse engineer. But the CFBF based Office documents are also basically just blobs of the older binary formats saved in a more structured way. The issues with Office documents have always been a question about their sheer complexity combined with their tight coupling to the internals of the Office programs. This still shines through in the OOXML formats which contains lots of stuff like "position something the way it was done in Word 5.0".