I published it [1], but only because I had to in order to use it without adding and approving it every time I started Firefox :/ I originally thought I had made the source available but eventually realized the code repo on Mozilla was only available to me (not sure what the point of that is). You just inspired me to get it up on github [2].
It's a pain to configure but the example JSON in the "Preferences" section of the add-on should be enough to get started. Just paste it into the textarea, save, then visit HN or Reddit, you'll probably see a few blank lines where links should be.
Right now, the top post on HN is a WSJ link. I don't want to see their links because I don't ever want to click them just to hit a paywall I already know I'll never accept. So my HN page looks like this [3].
The tool uses regular expressions on text and element attribute values. Anything that matches gets a given CSS style applied. I think it would be great if uBlock Origin could do this but it doesn't allow the level of granularity needed to accomplish the end result.
That sounds interesting. Have you published it or made source available? I'd love to try.