Not all escape sequences are implemented

[xPaw]

See the list here: https://github.com/ValveSoftware/GameNetworkingSockets/blob/8348e9234aba1b034f51ceff406a715de9ef61ad/src/tier1/utlbuffer.cpp#L54

The only strange thing to me here is \?.

[yaakov-h]

\? seems to be a trigraph oddity: https://stackoverflow.com/a/18156263/1994390