The subject of item categories in RSS feeds came up in an email conversation. While I have 'labels' I rarely use them except for certain, specific situations and this hadn't translated to categories in the feed.
I've added a quick check (only an additional 9 lines of code) to fetch any applied labels and write category elements to items where applicable. This post has the 'meta' label so I'll see if it gets passed to the feed as a category.
It worked Success!