This is common knowledge for long time readers of HN. However, it would be nice if the submission UX encouraged this. Prefilling the title with the <title> tag

This is common knowledge for long time readers of HN. However, it would be nice if the submission UX encouraged this. Prefilling the title with the <title> tag after the URL has been entered and making the title read-only with an explicit action to make it modifiable would go a long way towards achieving what you’re asking for. As it is, going to submission page does not make this guideline very clear. People see two input fields and simply fill them in as they feel best.