What does this article say is best for line spacing?

I would prefer not to click on an unknown link. Is there a reason you can't read the article?

So not only are you completely incapable of writing, you're also incapable of reading. You claiming to be authoring a book is like a paramecium claiming to be doing a fecking decathlon. 

And shove your thumbs down right up your jacksie, head. 

"Leave it to the professionals", though not in as many words.