HTML comment above metadata breaks date alias

Bug description

If I have the following as metadata, it interprets date: today as today's date and renders it into the final document, as per the docs:

---
title: "test"
format: pdf
date: today
---

## Quarto
...

If I add an HTML comment above the metadata, it no longer parses date: today into a date, and just writes "today" in the document instead:

<!-- test -->
---
title: "test"
format: pdf
date: now
---

Steps to reproduce

No response

Actual behavior

No response

Expected behavior

No response

Your environment

• very old version of Ubuntu

Quarto check output

quarto check

Quarto 1.5.57
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.2.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.41.0: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.5.57
      Path: [...]/quarto-1.5.57/bin

[✓] Checking tools....................OK
      TinyTeX: (not installed)
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: Installation From Path
      Path: [..]
      Version: 2018