I think it is an interesting edge case. My gut on this is that it doesn't depend on SynchroNet, but depends on the underlying server platform. I have a public key:

sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY29tAAAAIAAwPX8v4y4ccKfTnGYzHXfGjkUx4lohg04Y767M4dOyAAAABHNzaDo= lorenc@loren-vivobookasuslaptopx712dam712da