At the end of the day, your personal result will be for however you interpreted the instructions. But population-wide results should remain comparatively valid assuming each population is comparable in terms of being conservative/liberal with what they claim to know. E.g. you can still measure the difference between 25-year-olds and 30-year-olds because they're answering it in the same way collectively, and it's the differences I'm more interested in for research, than the absolute values.

I thought about making it something like a multiple-choice quiz, but it would have made the quiz a lot slower, and therefore either a lot longer or a lot less accurate, so checkboxes seemed like the only way to go.