Can I interest you in some homeopathic remedies or a bottle of snake oil? Maybe prayer? History is full of people who thought/think their bias and anecdotal evidence is good enough.
Not at all. I know people who tried homeopathic medicine and felt better afterwards, and swear by it. It is very much analogous.
The linked article is about objective measures of eye strain and health. Unless someone explicitly says otherwise, it's very reasonable to assume that they're also discussing those objective measures instead of subjective perception. If not - they're completely off-topic and they shouldn't be commenting here.
In particular, the comment earlier in this thread "I don't need to read other's research about dark mode to know how it lessens eye-strain. I have performed the experiment myself with my own eyes." doesn't say "my subjective perception of eye-strain", so we can assume that they're referring to the objective measurements, as is the actual topic for the thread.
The problem with "works for me" is not that that argument is invalid in and of itself. The problem is that homeopaths don't actually know that it works for them. What healed your infection and what did and didn't help is almost impossible to know.
Dark mode is very different. "do I have eyestrain after 4 hours of work" is easy to answer, and dark mode can be toggled with a single click to see how it affects you.