Consistency versus the user's Current Knowledge:

When you think about consistency, you’re thinking about the product. When you’re thinking about current knowledge, you’re thinking about the user. They are two sides of the same coin. We’ve just noticed that the designers who spend more time thinking about the users are the ones that end up with more usable designs.

Why do we gravitate to consistency? Because it’s easier to think about. You don’t actually have to know anything about your users to talk about making things consistent. You only have to know about your design, which most designers are quite familiar with.

Current knowledge, on the other hand, requires in-depth knowledge of the users. And that takes research time and investigative effort. It doesn’t come cheap, like consistency does. But it produces much, much better results.

...via elearningpost