I've never seen tip #4 (Rewrite negative conditions) or anything like it before. I can't see how that improves readability at all. If I saw it in a code review I'd ask the developer if they forgot to fill in the body of the if statement.
I've probably under-highlighted in this article the fact that each operation is intended to be used locally by a developer as an intermediate step during a refactoring of a legacy code. All these tips allow to transform a function to a new state #1, supposed to be easier to understand, and as a root point to perform some modifications in your code.They are just easy-to-implement solutions to assist developers with a messy code. Then, you can start implementing tests to avoid regressions and continue your refactoring to a newer state #2, which will then be commited on your Git repo.
Hope this can help :)