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dolphin is utf8 and needs this pregmatch

to disable/edit  it you will have to go admin/builders/fields builder and  on the join tab ikn the right...click on nickname/then click on advanced...in there you will see:

return ( preg_match( '/^[a-zA-Z0-9_-]+$/', $arg0 ) and !file_exists( $dir['root'] . $arg0 ) );

rewrite these rules or get someone who knows what they are doing to do it for you.

try deleting them and see what happen