If a site specifies a relative URL root, emoji files would omit the path from the URL, leading to lots of 404s.
At first, I tried to use
ActionView::Helpers::AssetUrlHelper.asset_url since this is what it's intended to do. But this helper function is extremely slow, and it took minutes to generate the URLs for the hundreds of links needed for each emoji.
Because emojis were broken in relative URL installations