And two hours later I can say, and this is where that block should go. I'm in control, not the program. That's clearly more powerful, more intuitive, and more flexible than any other method of text manipulation I've yet seen implemented in a word processor. Yet that's what WordPerfect, Microsoft Word, and others would force you to do. Over the years, it's become clear to me that writers work in unique ways.
Little things make a big difference to how effectively they can interface with their machines.
It's important that the writing tool adapt to the writer, not the other way around. WordStar is strong because it can fit me like a comfortable old shoe, and then make itself over completely to fit somebody else just as well. Finally, to come back to the keyboard interface, I think WordStar is the least modal word processor I have ever used. On a typed page, these tasks are quite distinct, especially with non-electronic typewriters. To change a word is a completely different spectrum of activities, and therefore a completely different mindset, from simply adding new words.