> Designers need to be careful to not give people rope for them to hang themselves with.

No, they don't. It's my system, and the look should be what I want it to be, period. What designers actually need to do is learn to respect their users, even when they disagree with the user's choices.

My teenager has their cell phone keyboard configured so all the symbols are replaced with cartoon cats. They can't type properly on it at all - I get text messages that are completely garbled - but they love that they can do this even though it actively impairs their functionality.

Some people like having ridiculously long fake nails that make it difficult to do their jobs (i'm thinking some checkout clerks I've seen who can't properly push any of the keys on their terminal), but it's their choice.