できた。
kita-0.177.2/kita/src/write/writeview.cpp

/* from, mail, message, bbs */ //-507
( ret += "&FROM=" ) += KURL::encode_string( nameLine->text(), mib );
( ret += "&mail=" ) += KURL::encode_string( mailLine->text(), mib );
( ret += "&MESSAGE=" ) += KURL::encode_string( bodyText->text(), mib );
( ret += "&bbs=" ) += Kita::BoardManager::boardID( m_datURL ); //-511
( ret += "&hana=mogera"); //-新512 *********************************//←この行を追加
/* key */
if ( m_mode == WRITEMODE_NORMAL ) ( ret += "&key=" ) +=