Anyway to apply CSS styling to items in an Ditto-powered RSS feed?

Your regular css file can style whatever the javascript loads up, so just hide the div class or id in your css file.

<div class="n-banwrap">

<!--- <div class="n-banwrap">

I don’t normally include styling in feeds and just leave that to the feed readers. Why are you including the navigation in your feed?

You can use custom tpl for the feed output and only include the items you want to post.

You could use a plugin to remove those altogether for the feed, onBeforeWebPageRender (or whatever that final event is called). No code hacking needed!

There are quite a lot of search-and-replace plugins in the Repository; any one of them should be a good outline of how to search for given strings and replace them (in your case simply remove them). Of course, you would need to do a check for the document’s content-type and only do the removal if it’s an rss page being generated.

Here’s an excellent example http://www.modxcms.com/ChunkReplace-837.html

if $modx->documentObject['contentType'] = text/xml {
...
}