The reason posts weren't being filtered is that removal only happens when the "All" option is selected in the popup settings. I know this wasn't explained anywhere, so I just released version 1.4.3, which adds a short description of this behavior right in the popup page, and also improves how subreddit names are parsed (you can now enter the full Reddit URL, "r/news", or just "news").
Could you update to 1.4.3 and let me know if filtering is more consistent using the "All" option? I don't have a GitHub repo yet (might set one up down the line), but feel free to keep reporting issues here in the meantime.
