Explain why to focus on the end-user's need, and/or moderate that advice

[jyasskin]

In w3ctag/tag.w3.org#39 (comment), in response to

Clearly articulate the problem that your proposed feature aims to solve from the user's perspective.

@chrishtr suggested

I think this needs more detail, and an example to show how it works. It also needs some sentences that explain why it's so important to start with the user-facing problem and not immediately get into the technical details.

We should also think through and explain how we want explainers to start from user needs when it's really a feature being designed for authors. E.g. CSS custom functions and signature-based integrity are primarily aimed at the second level of the Priority of Constituencies. While we need to ensure users aren't hurt, and there is some benefit to users from both of these, it's not inherently bad to add a feature for authors.

[mikewest]

On this topic, section 3.1 of today's FPWD points to mikewest/deprecating-document-domain, suggesting:

Sometimes the connection to the end-user need is complicated. Do explain the connection, even if this requires breaking the “be brief” rule. For example, see the explainer for deprecating document.domain, although even that could perhaps use another sentence explaining why security boundaries are important for users.

It would be helpful to flesh out this recommendation. What's missing from this example that would justify the value of origin-scoped security boundaries to end-users? Why is that justification necessary?

[mikewest]

Friendly ping. :)