Comment by Ekaros
10 hours ago
Headers, footers, notes, comments, alt text, probably dozen of other features. Documents often are lot more than just markdown so properly to support everything you do have a lot of ways to hide text for various use cases.
These are types of text that are, to some extent, effectively hidden. But I don't think that's what the article is talking about.
Word has a feature literally called "hidden text". Select some text, go to the font properties dialog, click "hidden" and OK, and watch the text disappear.
Edit: actually, this is white text on a white background as others have said, not true hidden text.