Forgive me I sound facetious, but aren’t highlighting and boldening, as well as italicising, underlining, and using red (or colours) for the font of certain parts of text all formatting features that have been around for yonks? And we know how to implement that kind of formatting, as @Meins points out for highlighting.
Having read Tiago Forte’s article, his point is not the special formatting per se, but the use of it to guide him in his progressive summarisation process.