For anyone finding this on a google search, DO NOT DO IT.
There is a reason behind the character limit.
For example, if you had:
- domainname1.com
- domainname2.com
Say you create one account 'domainna' (following the 8char rule) but for the other 'domainname2' (following the unlimited character username hack).
Then you log into 'domainna', you will see all databases from the account 'domainname2' as well as your own, because the databases in 'domainname2' start with 'domainna'.
My not be an expected issue for many, but I just had a client with full access to delete other users databases.. which they did, as they didn't recognise them!
For the average user this is not an issue but just because you CAN do something, doesn't always mean you should
Hope it helps!