I'd be glad to help you stop the auto-population when reviewing bank transactions in QuickBooks Online, @Defendu. 

The possible reason why this happens is that the cached saved by the browser allows auto-populating the information on your end. That said, let me guide you in performing some troubleshooting steps to resolve. Let's start by accessing your account using a different or a private browser. You can use either of these shortcut keys:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P
• Safari: Command + Shift + N
   

If it works successfully, you'd want to clear your regular browser's cache to prevent any unexpected behavior. Also, you can use other compatible browsers in QBO. 

Then, you can start reviewing bank transactions in QuickBooks Online. For detailed steps, please see this article: Categorize and match online bank transactions.

Keep in touch if you have other banking concerns with QuickBooks. I'll be happy to help you more. Have a great day!