The power of writing is that it is the way we formulate thoughts, opinions, and arguments. Language is the key way people frame their thoughts, and writing is one significant way to develop one's language skills. Writing is more than syntax, grammar, spelling and word choice--that's why you're not considered "unintelligent" for using a thesaurus or spell-check.
Anyhow, my entire point is "beating the comment section" isn't valuable as a threshold because as you hint at, it isn't really a place to find intelligent discussion.
None of those things were part of what they taught me at the mandatory school lessons, only at the entirely optional after-school "convincing communication" 45 minute session they had one time.
Actual school was basically "prove you actually read this Shakespeare play we assigned to you by mentioning some of these standard points".
As for comments sections… that they're low quality is the reason I chose them as an example, beating them necessarily improves the quality of global discourse - the people writing them don't recognise their poor quality.
Anyhow, my entire point is "beating the comment section" isn't valuable as a threshold because as you hint at, it isn't really a place to find intelligent discussion.