The Murder of Sonic uses Unity with the Mono backend, which means there's basically nothing stopping you accessing its files.
Hilariously, it also contains the Burst debug folder, although most of its content is correctly missing (probably due to whatever deployment procedure they're using)
Anyhow, it's thus very easy to find the name screen stuff. The game splits your entry into three categories: valid, inappropriate, and existing character.
The game does not allow you to name yourself any of the following "existing characters":