It's true social media such as reddit attracts marketing, but that doesn't mean everything that could be marketing is. The obvious problem with claims of invisible marketing is that they're impossible to disprove. Also, if shilling were nearly as prevalent as the original commenter asserted it couldn't be kept such a secret.

There may be real shilling on occasion, but the damage to constructive discourse from unverifiable shilling accusations seems greater than whatever the benefits of constant vigilance are supposed to be.

If marketing were really so seamless and even valuable, it would remind me of xkcd 810: https://m.xkcd.com/810/