ChatGPT vs. StackOverflow vs. Reddit in helping with a tricky web dev problem (mmkthecoolest.gitlab.io)

A developer asked ChatGPT, StackOverflow and Reddit to debug a CSS dark-mode bug after swapping a .header-bar div for a semantic <header>. ChatGPT repeatedly gave wrong or misleading explanations (claiming nesting wasn’t supported, recommending an ampersand, or blaming old browser bugs) and never converged; StackOverflow closed the minimally reproducible question as a duplicate/typo; Reddit quickly produced the actual fix. The incident highlights real-world tradeoffs: LLMs are fast but can be confidently incorrect, strict moderation can slow down help on StackOverflow, and looser communities like Reddit can be faster for pragmatic debugging. Technically, the bug wasn’t a nesting or browser-parsing issue but CSS specificity: the original selector list included .header-bar, which boosted selector weight so media-query dark-mode rules overrode light-mode rules. After changing .header-bar to header, the media-query selectors lost specificity and were overridden by the non-media rules, making links blend into the dark background. The correct fix was to increase selector specificity inside the media query (e.g., use descendant combinators like nav ul li a or target .current-section explicitly), or otherwise raise specificity. Takeaways for the AI/ML community: always ask LLMs for sources, verify model outputs against specs or tests, and use LLMs as accelerants—not unquestionable authorities—while combining them with human-reviewed forums.