Login vs. typeahead

[David Elliott]

We have a complaint that our system (like most versions of Unix)
doesn't handle users who like to type their password immediately after
their login.  Specifically, if a user tries to do this, some or all of
the password they type is displayed on the screen, and then this data
is ignored by getpass(), which flushes the input before it reads.

What I would like to know is if there is a good reason for the current
behavior, and if changing this behavior might in some way compromise
the security of the system.