I literally deal with accounting every day. I have used all of the major ERPs and implemented several of them, including Oracle, Netsuite, and Workday.

This website would not help a layman (i.e., non-accountant) or accounting student understand accounting, at all.

My issue with the website is not the use of credit/debit vs negative/non-negative numbers. My issue with this website is that it presents transaction flows without properly explaining the accounting logic of those transaction flows to its intended audience and even then it's way of framing transaction flows only works for the simplest transactions. The website's chosen way of explaining accounting would be actively harmful to understanding more advanced accounting issues. It would be like trying to teach someone how the internet works by framing everything in terms of plumbing.