Suggest situations where it is unwise or impossible to provide a consistent user interface.

What will be an ideal response?

A consistent user interface may be impossible to produce for complex systems with
a large number of interface options. In such systems, there is a wide imbalance
between the extent of usage of different commands so for frequently used
commands, it is desirable to have short cuts. Unless all commands have short cuts,
then consistency is impossible.
It may also be the case in complex systems that the entities manipulated are
of quite different types and it is inappropriate to have consistent operations on each
of these types.
An example of such a system is an operating system interface. Even MacOS
which has attempted to be as consistent as possible has inconsistent operations that
are liked by users. For example, to delete a file it is dragged to the trash but
dragging a disk image to the trash does not delete it but unmounts that disk.