Since the group remains as 'mysql' the mysql process is still able to grow the table file(s) without problem. The quota limitation is applied against the owner of the process, which in this context is not the user.I have a question about the "/scripts/updatemysqlquota" script. In looking at the code it basically chown's the database files to be owned by the account user-id and group mysql. From memory chowning the db files to anything other than mysql caused a lot of problems. The basic issue (again from memory) was that when the cpanel account went over quota mysql could no longer write to the database. mysql then 'hung' trying to perform the database write. This then totally hung mysql until you either restarted mysql or gave the account more quota.
Has this been 'fixed' with the latest version of mysql or is this still a nightmare lurking out there?