How are these two user drops different? Other than the obvious, what is the difference between:

drop user user_01@host01;


and

drop user 'user_01'@'host01';


In a sample test, they both achieved the same result. From Account Names docs (5th bullet point), looks like they are not the same ... yet they appear to do the same thing ... ?

MySQL 5.5 on Centos 6.x.
They are identical.

The bullet point you mention states:


  The user name and host name parts, if quoted, must be quoted
  separately. That is, write 'me'@'localhost', not 'me@localhost'; the
  latter is interpreted as 'me@localhost'@'%'.


And that is what you did, you quoted them separately. In other words, all these are equivalent:

drop user    user_01@host01;

drop user   user_01 @ host01 ;

drop user  'user_01'@'host01';

drop user 'user_01' @ 'host01' ;




And if you wrote:

drop user 'user_01@host01';


... it would be interpreted as:

drop user 'user_01@host01' @ '%';