When “Hotlink Protection” is on the article image is downloaded by Discourse to display in the onebox but the favicon is not (in Firefox this is clear as there is an empty box):
How would you do that? And if someone had gone to lengths to see that you can’t download those images my response is either “serves them right” or “I will respect their wishes.”
Lo único que pregunto es: ¿tendría sentido tratar los favicons de la misma manera que otras imágenes —descargar copias y servirlas localmente?
Prueba el comportamiento actual tú mismo: activa la «Protección contra hotlink» en un sitio detrás de Cloudflare y descubrirás que Discourse sigue descargando las imágenes principales para los oneboxes…
They will as long as they are in a format your Discourse accepts. The example in OP is using .ico, which is an old format not allowed in Discourse by default. You can add it to the list in your site.
I added .ico to authorized extensions and rebuilt the HTML of a post and while the favicon wasn’t downloaded and served locally straight away it was when I checked it a couple of days later.