I mean, is HN really an unbiased sample source? Ask my mom or grandma if she prefers dark mode over light mode and she’ll say whatever she has right now on her phone.
My mother on the other hand is younger and still has an adventurous willingness to try new things, and last I saw was using the dark mode in Windows 10.
Polling someone who likes light themes because they know no better is an answer to a completely different question.
Also, while trendy, "bias" isn't a word you should throw around unless you also have established the question being asked and what the bias is. Informed answers to the poll aren't biased, especially compared to someone who doesn't know what a dark mode is.