Kind of, although more like reddit's "hide" feature. There's also a GM script to do like the extension you link, but it has menus so there's no need to edit an array. No time to find link but it will be on userscripts.org somewhere.
> I mostly did it because it was a fun exercise in javascript
Me too :) Although I'd recommend using jQuery if you have time to learn that as well. Makes DOM-related stuff easy so you only need to roll code for the things which are unique to your app.
I'm actually taking the opposite approach... I started using jQuery to do all my DOM related stuff, but now learning actual javascript for the fun of it. It really is a surprisingly flexible language.
