It's not just that it was lengthy - chat transcripts like that are difficult to read and contextualise properly, even if posted in full, and also even when shortened to what one of the participants finds to be the most relevant. Reading through it is like scanning the script of a play looking for a specific quote that stitches the scene together, and never finding it. I'm still not sure what you're looking for from the forum members. 

Re: this particular point, though: Chat with eBay Billing Department about difficulty substantiating whether or not they have charged or refunded a non-sale final fee, where it is stated and how to find out if it was followed through on.

If it's an unpaid item, one of the things you can do to test if they're applied is open your account showing the current outstanding amount. Then open a new tab to access and close the UPI. Once it's closed, it will say "check my fee credit". Click that and it will take you to your account and display the new total. You can switch between tabs and check that the new total is reduced by the appropriate fee credit. It's possible, but a little more difficult, to do that with cancelled transactions. 

Full invoices from eBay list both fee and credit tallies as a single line item, as well as fully itemise them underneath. Even if they put the history there sequentially, those totals wouldn't change and you'd still have to go through every fee charged and every credit provided in order to actually check their math, or you can subtract the credit tally from the fee tally and see if the final invoice amount matches.