I would like to remark that sad as it is, .doc and .docx are two wholly different use cases. For about a year in my old job, I was the only one who knew that the contract writing software didn't in fact accept docx-anything, so I converted it behind the scenes.
The "expectations" remark (paragraphs!) is about right.
If you're dealing with dead files that by all rights should open, you're already in trouble. The rest is guessing hoping you get lucky. Some ideas:
A. Try to write as a Rich Text RTF file. Sometimes that's a middle ground to pure text.
B. Change File Formats.
Sometimes X native program refuses to behave but Y or Z "import" function works. Not to be sloppy, but in this category just save a "scratch" copy to play with, and abuse the scratch copy as aggressively as you like, since you're looking at Data Zero on the real copy, who cares? Typical tricks include just changing the file ending of the copy to .rtf, ignore the crap and save 38 of the 50 important lines of text! Other tricks include opening in custom semi-custom software, and more.