I really like the concept. I think users are completely outmatched when it comes to social media. The big platforms have literally thousands of super smart people working to make their products sticky. All we have is our caveman brains that didn't evolve for this. I don't think regulation is the answer — we need smart tools like this that help us control how we use the platforms.

I tried out the extension now and it seems to work well. Great job on it!

I'd recommend changing the placeholder content for "Block Tags". "Enter a Keyword" made me think it would filter exact matches but it's actually filtering based on semantic meaning. Keyword also makes you think it needs to be a single word and not a phrase...

IMO the free tier is a bit too restrictive and doesn't give a good sense of the full value of the product (e.g. you'll lose someone who isn't on Twitter but wants to try it for Reddit). I'd suggest either opening the free tier up a bit, or moving to a trial rather than freemium model.

All in all, really well done! Hoping this is successful