I agree with almost all of the specific examples you give, but I think I agree _because_ those UI decisions work better for customers, and not because they are absolute right and wrong. I think I can illustrate this with some examples:
1. Consider a keyboard without an f-key, eg Arabic. If the user is using an Arabic keyboard, what should bring up the browsers 'find' functionality. Of course ctrl-f won't cut it. Perhaps it should be ctrl-[first letter of 'find' in Arabic]? Or perhaps ctrl-[the letter in the same position as f on qwerty keyboard]? It makes sense to follow convention if one is already established for Arabic, but then what about languages that are new to the web?
2. Consider a phone-tree, which is a sort of UI. For this UI, the 'absolute right answers' of minimum text contrast, font size, keyboard shortcuts, etc, make no sense, but there are surely other ways to make the UI work well for customers.
In both these scenarios, I feel the 'right' choice is to pick the UI that is best for users. I think there isn't a-priori a right answer, and users habits change over time and across cultures, so it's not necessarily an easy choice.
1. Consider a keyboard without an f-key, eg Arabic. If the user is using an Arabic keyboard, what should bring up the browsers 'find' functionality. Of course ctrl-f won't cut it. Perhaps it should be ctrl-[first letter of 'find' in Arabic]? Or perhaps ctrl-[the letter in the same position as f on qwerty keyboard]? It makes sense to follow convention if one is already established for Arabic, but then what about languages that are new to the web?
2. Consider a phone-tree, which is a sort of UI. For this UI, the 'absolute right answers' of minimum text contrast, font size, keyboard shortcuts, etc, make no sense, but there are surely other ways to make the UI work well for customers.
In both these scenarios, I feel the 'right' choice is to pick the UI that is best for users. I think there isn't a-priori a right answer, and users habits change over time and across cultures, so it's not necessarily an easy choice.