Please don't scold someone who's already in a shitty situation, or lecture them with the obvious. That breaks the HN guidelines, notably this one: "Be kind."
It's extremely easy to do this kind of thing on the internet and not as easy to realize the effect it has on people, and also on the community.
What the purpose of your comment? It's not helpful.
If that weren’t the case, I agree with you, it’s a good message to spread.
Run this:
youtube-dl https://youtube.com/c/MyChannel
and have a snack while it finishes. You'll thank yourself later.
I think it's important to mention that such trust is misplaced and risky, ALWAYS make backups. Sure it's generally common sense for many, but the OPs story is a nice example.
I don't think that that's particularly true of HN readership though.
If GP's comment was on a more mainstream forum e.g. Reddit, then I would agree with you, but as it stands it feels a bit gratuitous.
In other words, the next generation of normies will probably understand this because of people before them learning the hard way.