[m-i-l]

I used ST Writer which came bundled with my ST. I still have all my ST Writer files (last modified in 1993!), and quite impressively they open just fine in LibreOffice with formatting and everything preserved (unlike some later .doc files I have).

[p_l]

.DOC was never meant to be interoperable, even across Word versions (much), you were supposed to save "final" or "exchange" versions in RTF :)

[klondike_klive]

That is genuinely remarkable! Even indentation?

[m-i-l]

Yes. Just opened some files to check. There was one including a table which I thought at first was a little wonky, but then I realised the column that looked off had currency where I'd right aligned on the decimal point, so even that seems to have been preserved!