The area that seemed gray here particularly was the "internal decisions part." As someone who has designed maybe... 40+ interfaces, I know the tremendous amount of effort and thought that goes into the simple placement of a button being on the left or the right, with huge impacts to usability and user experience.
So when he posts a few images of other sites that "look" similar, I don't quite buy the fact that he didn't liberally borrow from the many hours of decisions by Repli. Thats purely a guess though, and I could absolutely be wrong.
I would imagine it would be easy for the author to rationalize it in his head that "well, lots of other sites have a button in the top row I can do it too!" and in effect, ends up copying a lot of Replit features without innovating on them simply because other sites "look similar"
I picture myself as a CEO seeing a previous employee with something that is very clearly using a lot of the decisions we worked out together, and then see a list of 20 bullet points trying to rationalize why it's ok, that would be super irritating to me, but that would be the limit of it. Definitely not worthy of anything more than a polite conversation, that's for sure.