“A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines.” — Ralph Waldo Emerson

The big difference is that Emerson qualified his statement. Consistency in UI is rarely foolish. Consistency in code, likewise. But absolute consistency is not something to strive for when it means constraining design or usability.

And don’t let consistency hinder improvement. Where I work, there are plenty of perfectly consistent policies and procedures that simply don’t work. We keep using them because ‘we’ve always done things that way’.