So this is kind of bizarre wording on the author's part. He describes that in fact Reddit does use time decay for exactly the reason you mentioned literally two sentences before what you quoted. It seems weird to state something as a fact then dispute it based on an anecdote without addressing the obvious tension between those things...

> Reddit’s ranking algorithm attempts to rectify this by determining comment ranking using both time and community voting; comments in a thread, by default, are ordered based on the points score (upvotes - downvotes) the comment receives, subject to a rank decay based on the age of the comment.

> In theory, this system should allow comments that posted later in the thread’s lifetime to rank much higher temporarily, then Redditors can vote on the new comment; if the new comment is good, it can now rise to the top and therefore the content which would otherwise be buried is now surfaced.

And then it continues on to the section you quoted. I'm not sure what to believe!

I commented about the HN behavior in another thread. (I did not comment about the HN behavior in the article because I have no statistical evidence of HN behavior.)