MathML’s mspace element by a self‐closing tag <mspace ... /> gives a warning to use <mspace ...></mspace>

[Paalon]

Describe the bug

When I use self‐closing mspace tag in MathML in HTML <mspace .. /> in Svelte, it gives the following warning:

3:54:26 PM [vite-plugin-svelte] src/routes/+page.svelte:11:1 Self-closing HTML tags for non-void elements are ambiguous — use `<mspace ...></mspace>` rather than `<mspace ... />`
https://svelte.dev/e/element_invalid_self_closing_tag

but the examples of mspace element shown in MDN web docs and MathML Core, W3C Editor's Draft, 02 April 2025 use the self‐closing tag expression. Therefore, the warning doesn’t seem appropriate.

Reproduction URL

https://stackblitz.com/edit/vitejs-vite-ndwypfdq?file=src%2FApp.svelte

Reproduction

1. Create a Svelte project by npx sv create ⟨project name⟩
2. Use <mspace ... /> in MathML in HTML in Svelte.

Logs

System Info

System:
    OS: macOS 15.4
    CPU: (8) arm64 Apple M3
    Memory: 88.20 MB / 24.00 GB
    Shell: 4.0.1 - /opt/homebrew/bin/fish
  Binaries:
    Node: 23.11.0 - /opt/homebrew/bin/node
    npm: 10.9.2 - /opt/homebrew/bin/npm
    pnpm: 10.7.0 - ~/Library/pnpm/pnpm
  Browsers:
    Safari: 18.4