[TeMPOraL]

I don't think it's buggy, but it's probably too simple. From my observation, it just starts the counter on any HTTP request (with appropriate session data in it, of course). This means if you have HN open on a mobile phone and/or you have lots of tabs, there may be spurious reloads happening even when you're not looking at the page - all of which will start the noprocrast timer.

[0xCMP]

Yep. I had mine at like 30m and then 120m block and so if I accidentally loaded it like you said I would be like "oh crap this is my chance!" and load every single story I could into tabs before it would block me. Mobile is a great example but also when Chrome has a tab but it isn't loaded in memory anymore.

It did work, but it had some counter intuitive failures too.