There are some restrictions on the characters that may be used in login names, full names, group names and the like. If your name contains unrecognised characters (for example, letters with accents) you will just have to type it without.

Login names and group names

These may consist of alphanumeric characters (letters and numerals) and any of the following:
     .   -   _
They may not contain spaces, and all letters must be plain, without accents etc.

Full user names and "contact" names,

These may consist of alphanumeric characters, the SPACE character, and any of the following:
     .   -   _   '   "   ,   ^   +   =   (   )
Again, the first and last characters must not be spaces, and special versions of letters, with accents and the like, will not be recognised.

Addresses

These may consist of alphanumeric characters, any white space characters such as spaces, tabs and newlines, and any of the following:
     .   -   _   '   "   ,   ^   +   =   (   )
The first and last characters must not be white space, and special versions of letters, with accents and the like, will not be recognised. Other characters, including the colon, hash, arabas, dollar, square brackets and curly braces are not allowed.