I finally (re)located a website I used for a lot of basic Word-to-markdown/plaintext conversions before I discovered how good iA Writer did it. I still use it sometimes, when I'm away from my main machines, and it will be an important bullet point in a course I'm teaching on markdown at the next residency.
Basically you just browse for the file you want to convert, hit convert, and you get a page with clean markdown to copy-paste into a new text file. I really can't believe there aren't more web scripts that do this, but there aren't, so this one is definitely worth a bookmark.
Word to Markdown Converter
Word to Markdown Converter. Converting a Word Document is as easy as 1, 2, 3… Step 1. Upload a .docx or .doc file. Drag-and-drop the file below to upload. Step 2. Get back crisp, clean Markdown. # H1 Paragraph ## H2 Paragraph ### H3 Paragraph. Use it on GitHub or elsewhere. Step 3 …