I don't usually see many comments like this, which "downvote knowledge" as you say.
Instead, I see comments arguing that the emphasis placed on that knowledge is wrong-headed or misplaced.
For example, knowledge about data structures is a great thing. But defining an interview process with data structure trivia as an implicit standard for hiring someone is bad, and is a good teachable moment for pointing out why it's a silly way to filter candidates.
Similarly, detailed knowledge about advanced statistical methods is a great thing. But it's silly to force candidates to fill resumes with buzzwords or treat their stats knowledge like peacock feathers because those are the hoops to get hired, when then in reality the work will be 90% data engineering and devops. It's similarly a teachable moment to point out why an emphasis on these methods is silly, unless you're in a business that actually plans to give an employee projects and tasks that require these things.
I guess if I saw a comment that truly was dismissive of the knowledge, in and of itself, then I would agree that is worth downvoting.
I honestly can say I've not seen that very often, though. Only comments reacting to that way signalling effects are used to subvert the knowledge for e.g. silly hiring trivia or data science credential.