[throwaway14356]

I keep wanting to build a PICS rating service and (humorously) add it to my feeds.

https://www.w3.org/PICS/

The use as parential control is clutter to me. The referring to content selection as filtering was a terrible idea.

The content labels can exist on a different website, they can live in the html document and there is an rss element specifically for it.

You make up your own rating label and put a score behind it. There was an example for example that rated by canadiannes

https://www.w3.org/TR/REC-PICS-labels/#Example

As usual they spend a lot of words explaining something simple.

In its almost most simple form:

(PICS-1.1 "http://www.example.org/ratingservice" label for "http://www.example.com/foobar" rating (javascript 5 php 4 mysql 6 bloomfilter 10))

Looks a lot like hand crafted weights to me. If widely adopted you could make a fascinating tag cloud from your 100k rss subscriptions.