I hadn't heard an explanation for why authors might use one tense or another for writing. That makes a lot of sense though.
I appreciated your comment about not deleting your work. That's how I approach it, but I think it's important that people remember their work isn't garbage if they made mistakes, it's just in the process of coming out. It takes time to be revealed. I normally push the paragraphs down and start writing at the top. I'll pull elements of the previously written paragraphs into my current version, and then delete the rest when I've used what I needed. Works very well for me.
That poem is maddening! I was trying to remember that it's an example of what not to do, but it was still hard to not get upset. :)