How are you viewing the CSVs you posted?
When I look at the one with Comments in Excel (2019) I don't see lots of commas. Some are shown as a very long line. Other's have a lot of preceding white space and then the text, wrapped according to the Excel column width.
In my experience that is the way of downloaded "Comments". The HTML is inconsistent at best, but just as often it's a shambles. I've never found a 'foolproof' way to make them consistent other than:
- copy the HTML to clipboard,
- clear the Comments (Ctrl+A, Del),
- paste clipboard into Notepad++,
- fix the HTML to be consistent & simple (I start by removing most of the tags),
- test in a browser,
- copy and paste from Notepad++ back into Comments.
But that's probably not a viable option if one is dealing with zillions of books
BR