Especially in Korean Wikipedia, default autoblock duration (1 day) is almost not effective to persistent vandal because once blocked for inappropriate username then tomorrow he create another one easily. And the block-create loop goes for very long time. I'd suggest to make ultra-autoblock (about 30 days) option and give sysops the right to apply ultra-autoblock. Best regards.
T19929: CentralAuth account locks should trigger global autoblocks
T43479: [Spam/vandalism] Raise $wgAutoblockExpiry noticeably