Seems like a bug, so I'm reporting it as such
Version: [UNSTABLE 42.15.3]
Mode: Multiplayer
Server settings: Host
Mods: None
Save: New
Reproduction steps:
1. Host a server with any settings or mods (noticed on modded, verified broken on fresh, default server settings with no mods)
2. Attempt to set access level to admin with /setaccesslevel "Free Flyin'" "admin" which always worked previously
3. Commands returns Invalid username "Free Flyin'", fails to promote me to admin or any other level.
No characters are illegal, as "FreeFlyin'" and "Free Flyin'" substituted for username are both accepted (but do not promote me since they're not my username). Substituting Free Flyin' without quotations does not work (as expected). Doesn't seem like an escaped string given these, so I have no idea why it's not working.