Module use raw data for SSL_CLIENT_{S|I}_DN_x509 environment variables. If an certificate contain distinguished name item encoded as BMPString and universalString this item cannot be used in neither in LogFormat nor in SSLRequire. By example such items are logged as - in log file. Since BMPString and UniversalString are included in RFC 5280 for backward compatibility severity is set to minor.
For 2.4, this was addressed with the changes in r1054323 - see also the thread "Re: SSLRequire & UTF-8 characters & backward compatibility" on httpd-dev: http://mail-archives.apache.org/mod_mbox/httpd-dev/201012.mbox/%3C201012190158.28169.sf@sfritsch.de%3E I think it's unlikely that this is ever going to be backported to 2.0.