But http://docs.basex.org/wiki/Serialization#Version_7.1 says newline is in. You might want to revise that.
Yep, the "newline" parameter only specifies if \r, \n or \r\n will be chosen as end-of-line marker. Instead, you'll need to work with the "separator" parameter, which allows you to change the character which is used as item delimiter.