Ensure as much formatting as possible is sane in RSS output

[Athanasius]

Need to check at least the following for looking sane in RSS output. The issue is that most RSS readers strip all element attributes, so can't style things, have to rely on basic things like using blockquote or pre elements.

• [code] elements. Try mapping them to <pre>...</pre>.
• Various 'media', like images and videos.
• [spoiler] sections ?