The Markdown syntax used by the forum is documented here:
https://s9etextformatter.readthedocs.io/Plugins/Litedown/Syntax/
Syntax highlighting for code blocks marked with a language is not currently supported because it depends on enabling the BBCode extension and injects inline styles and scripts forbidden by our Content-Security-Policy.
We disallow external images in our Content-Security-Policy for privacy and security reasons. We've provided a caching image proxy as part of our server to work around this. The content types we support are AVIF, JPEG, GIF, PNG, SVG and WebP. Other content types aren't currently supported but can be considered. At the moment, the only permitted domain is i.imgur.com. The proxy only permits discuss.grapheneos.org as a Referrer to disallow hotlinking elsewhere. Opening images in a new tab or saving them will work, but copying the URL into another browser tab will result in a 403 error.
You can use the image proxy by replacing the URL with https://discuss.grapheneos.org/media-proxy/URL_WITHOUT_SCHEME_PREFIX. For example, the following syntax works:
It turns into this:
Our image proxy implementation is available in our repository for discuss.grapheneos.org.