That reasoning does not apply when the person (or the automated system) watching for spam has an O(1) way to get a notification of the next new comment, such as for example refreshing <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;newcomments" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;newcomments</a>.