I think you've got this a little backwards.

The target audience of this comment chain is exactly people who are familiar with Tailscale, aren't familiar with Iroh, and read the linked post.

Such a person (like me) reading that post will have an immediate reaction of "this sounds a lot like Tailscale", but the post doesn't provide a clear answer to "what problem does this solve that Tailscale doesn't?"

The people with that reaction are the target audience of this comment chain. The fact it is upvoted to the top of the comment section here is an indication that there are quite a few such people, and if this is your reaction you're presumably not one of them. (and that is perfectly fine!)

Tailscale is a very well established company in the field, and if you didn't hear tailscale before, perhaps this product would not be so interesting for you, so it makes sense here.

Otherwise, everything would end up being a "Thing Explainer"[0].

[0]: https://en.wikipedia.org/wiki/Thing_Explainer

A big part of communication is knowing your audience. GP could have spent a bunch of time explaining what an "application" is, what a "network" is, etc. but he knew that most HN users are familiar with Tailscale, so leaning on that prior knowledge let him explain the concept in fewer words. That is effective communication.