The full range of everything we do is available to anyone who asks. You have to email hn@ycombinator.com, as the FAQ explains (https://news.ycombinator.com/newsfaq.html), but there's no restriction on whom we help, or how. We help people who have abused this site for years and then ask us (sometimes exceedingly impolitely!) to clean up what they did, and we treat them the same way as we treat anyone; I may grit my teeth while doing it, but that's all. Why? Because it's best for the community in the long run if we treat everyone the same way, and because—as I tell users who email—we don't want anyone to get in trouble from anything they posted to HN.
Even more than that, one of the administrators previously told me via email that HN is not able to rename accounts (presumably they use account names instead of numeric IDs as a key somewhere). So the only explanation for the displayed author on that post having changed is that they switched the author of the post, the original author's account could not have been renamed.
Either that email was many years ago or something got confused, because we rename accounts for users all the time.
In fact, when we developed that feature, I replied to everyone who had emailed over the years asking for it, asking if they still wanted it. If you weren't on that list, your email must have been many years ago.
Edit: oops - I see I neglected the important thing. If you still want your account to be renamed, please email hn@ycombinator.com and we'll be happy to help!
The account creation date for user _pecl is also the same date the comment was made so maybe it is possible to make a new user, change their creation date, and also change the attribution of specific comments to that user?