Blocking mode not working with WhatsApp I own a Samsung Galaxy S4, which has the Blocking mode feature.
It is very useful because it mutes notification sounds during certain hours (I use it to automatically keep my phone quite while I'm sleeping).

It works perfectly for all the applications but WhatsApp.
It seems to be a known issue, and I found a workaround that involved a led notification management application.

I don't like that solution because it is not clean and I'd like to find a better one.
I come from the iOS world where all the applications are forced to pass through system notification center and I can't really get what's happening on my phone nor how WhatsApp can deliver me notifications.
It looks like a Whatsapp problem. Your best bet would be to raise this concern with Whatsapp themselves. There's no guarantee that they'd fix it, but this isn't Google / Android issue either (from a general perspective). Developers should follow "best practices" when developing Android apps.

UPDATE 2013-10-07: This issue has been discussed in XDA, and it's because of how Whatsapp handles notifications (no specific details given). In that thread, there is a possible solution using the Light Flow app.