2017-07-21 17:27 AEST by Arthur Barrett - The 'cvs passwd' command should give some hints on case sensitivity:

Client 'add operation':
- when $CVSROOT is remote:
  "Warning: CVS usernames are case sensitive"
- when $CVSROOT is local and not Windows:
  "Warning: CVS usernames are case sensitive"
- when $CVSROOT is local and is Windows:
  "Warning: CVS usernames are case sensitive:"
  "          DOMAINS should always be UPPERCASE"
  "          usernames usually are lowercase"

Server (add operation):
- when is Windows:
  if username is not lowercase:
     "Warning: CVS usernames should usually be lowercase"

Server (add or update operation):
- when is Windows:
  if domain (password that starts with !) is not UPPERCASE:
     "Warning: domain names should usually be UPPERCASE"

2017-07-21 17:34 AEST by Arthur Barrett - This is related to lots of other issues, see:

Bug 5052: preserve case with WinBind auth on Linux/Unix (fixed in 2008)
Bug 5196: Support for case insensitive usernames on Unix
Bug 6989: passwd is case sensitive
Bug 7004: Doc typo discussing SSPI allows any user able to spoof auth domain 
users
Bug 7178: Case sensitive usernames in passwd on Win systems