Anything where you would not want the current paragraph to become detached from the next. The most common use would be in non-sectional subheadings. You wouldn’t want “12.8 Copy and Paste” to end up all by itself at the bottom of a page, but rather always be attached to the paragraph of text following the heading. I’m not sure how you ended up with sporadic instances of it—probably copy and paste. Since the code is invisible, that can happen.
Here is the thread URL if you need it.