It's a bit difficult to explain...
Back when the site first started, the text was saved in a different encoding. This caused (and still causes) text issues on some browsers. So, newline codes would probably be displayed fine but the backend thinks otherwise, and we get text without linebreaks.
When people edit listings with this oddly saved text, the backend sees that the encoding was changed between what's on file and what was submitted, and so it asks us to approve or deny the change. I usually approve it because you're unintentionally fixing the text so it's saved correctly. So yes, it's a bug, but it's a good one. No need to worry about it.