HN mods can confirm this, and cx42net (or any other submitter) is encouraged to email mods at hn@ycombinator.com for this or other issues. I'd done so myself on a recent submission that was autokilled.
As for ScienceAlert, looking at submissions from the site strongly suggests it's banned:
<https://news.ycombinator.com/from?site=sciencealert.com>
That can be lifted for specific instances on request.
Though in this case, the disambiguated link from The Conversation would be preferred: "Please submit the original source. If a post reports on something found on another site, submit the latter."
<https://news.ycombinator.com/newsguidelines.html>
