I was composing this post and later noticed that one paragraph did not wrap right (e.g wrapping in the middle of a word or way too early).
The regular "Rich text" editing window did not show anything visibly wrong, so I switched to HTML view. To my surprise, that paragraph had " " between almost all of the words. (The other paragraphs were fine).

Can anyone explain how this happened? I don't remember doing anything unusual.
Here's how the paragraph look in HTML view. I was able to painstakingly remove all that extra garbage. What generated it?