I think it's disingenuous to use affiliate links if someone said, "Hey, where can I buy a Kindle?" or "what's the best ebook reader I can buy online?". But in this case, if you saw this link and said "Oh crap! This is news to me and I've been waiting for a price drop" . . . then by all means kirse deserves an affiliate payout.
In my opinion, lines are crossed when you suggest a less than optimal solution/link because it'll earn you more money. For example - on my NIN site, when an album becomes available for pre-sale, I list each vendor that we find along with their price, even if they're selling it cheaper than Amazon. If I were to ONLY suggest Amazon for pre-orders when I knew better deals were to be had, that's where I feel one starts losing ethics points.
I think the bottom line, for a site like HN, or a message board, or anything like that -- it's up to the owner/administrator of the site. I don't know how much work goes into the administration of HN, but the content is almost entirely crowdsourced. Were it my site, I'd probably strip (but not replace) all affiliate code from links, but I don't really think it's unethical to have posted that to HN with a link. Were it me, I'd have commented in the interest of full disclosure.
And that's pretty much all I was doing with my first post - disclosing something that may be of interest to readers here :)
I just wanted to comment mainly because I always see people going way out of their way to disclose affiliate links (and conversely -- people pouncing on undisclosed ones like they've found a witch) and I always think "do people really get so offended by them?". But yeah, I totally agree that it's wrong to recommend a sub-optimal product b/c you're an affiliate.
2. Get people on mechanical turk to upmod your submission until it takes off
3. Profit?