Rated 4 out of 5 stars
It's useful, but there are 2 major sites/groups of sites on which it has some big drawbacks: 1. youtube - it blocks your inbox too. I tried *.youtube.com/inbox* and some other combos but it doesn't work; if I mark this domain safe by clicking the icon it shows all the comments on videos sadly; 2. io9, gizmodo and the sites like them. It blocks the whole page or it shows the whole page, including the comments. Please make it support those sites or at least post how to use the youtube inbox without showing all the comments on video pages or turning it on/off every time a message is received or must be sent.
LE: I've read your reply, thanks for the fast input. Well, I get it although i don't understand why the youtube inbox can't be excepted from filtering as it seems to have a unique url, with *inbox* in it. But anyway - thank you!
Unfortunately, it's simply not viable to implement website specific rules as one would have to work with that indefinitely because of the internet's sheer size. The addon will filter out what looks like a comment in the HTML/CSS markup provided, and most sites does this "properly".