Although I don't disagree with your thought here and that was actually the podcast host's/other contributor's original hunch too, this wasn't actually an issue

Although I don't disagree with your thought here and that was actually the podcast host's/other contributor's original hunch too, this wasn't actually an issue with interpolation. I know it sounds bizarre, but the paraphrasing of the podcast hosts and comments from the infotainment system code author suggest that he was treating all strings as percent encoded[0] without any checks or guards in place. Since "% I" isn't a valid character reference, it chokes on it. [0]: https://datatracker.ietf.org/doc/html/rfc3986#section-2.1 https://datatracker.ietf.org/doc/html/rfc3986#section-2.1