Exploitative? Of who? The submitters?
I only ask because as both a submitter and content creator I have zero problem with anyone finding items through /newest and sharing them wherever they like, credit back to HN or not, and am unsure who benefits from dissuading this.
Oh, this is an interesting qualifier. The newsletter is not based solely on HN. There are other sources as well. How much is from HN? I'm not actually sure myself, but I'm gonna attribute some HN links (where applicable) and we'll see.
Whatever sources you're systematically drawing on, each deserves acknowledging. By "systematically" I just mean that when people randomly pass around one-off links to random articles, there's no need to be particularly scrupulous about provenance, but when they're building projects on other platforms, that's different, and then there is such a need. Otherwise the balance between giving and taking is out of whack.
The "taking", in this case, is using HN (and other aggregators) as a source of links to interesting stories; this needs to be balanced by some "giving", and on the web, the well-established way to do that is to link back to the place you found it. That way, good things can flow in both directions: your readers get interesting things to read, but they also get to know about a community they might like, and the community has a chance to gain new readers who might enjoy it.
If you don't do that, then the claim you're implicitly making is that you scoured the entire web looking for those articles, rather than drawing them from other aggregators that already did that. That woudl be false and misleading—it's "taking" too much, in the above sense. What you're actually doing, which is looking at existing aggregators to find good content that got overlooked there, is (a) genuine work and (b) a wonderful contribution—and that's the work and contribution that you deserve and should take credit for. I don't mean to criticize that or minimize it! The existence of many good articles that get overlooked shows how much it's needed. It's simply that each contribution needs its proper acknowledgment.
Btw, it's been on our list for a good 7 years to ask people to confirm that they've read the rules before posting a Show HN, but I always hold back because it would break a certain precedent. HN doesn't tend to use nag screens and so on.
Newsletters can't be Show HNs. Please read the rules—they mention this explicitly: https://news.ycombinator.com/showhn.html. I've replaced "Show HN" with "Tell HN" above.
Also, if you're getting these stories from HN then I would ask you to link to the HN submissions.
We totally support the goal of bringing attention to great stories that haven't gotten significant attention yet. Other people have worked on this problem (e.g. https://news.ycombinator.com/item?id=23392049), and in fact we spend a good deal of time doing the same thing (https://news.ycombinator.com/item?id=26998308). But it's not good for community to sever the links to the source where you found them. In fact, at first glance it felt exploitative to me—a bit like kicking the ladder out from under you—but on reflection I'm sure that's not what you intended.
If you include the HN sources the way that polote has done here: https://hnblogs.substack.com/p/hn-blogs-24121, that would suffice.
p.s. It looks great and I'm going to subscribe!