Ferryman-san can, I believe, but they won't. We found them in a cavern marked with a lantern--you could call that a symbol for Ferryman-san, couldn't you? According to them, we can't read them because we aren't connected to the group who wrote this.

[Nagito having information squirreled away like this is probably not that surprising to someone who watched his behavior in the simulation. But at least this probably doesn't have anything to do with murder.]