Sometimes, I don't get notified if someone addresses me using "@username" in either a thread where I have posted or below one of my posts. At first I thought it's me missing the pings when I get several at once but it's definitely not.
The other thing about notifications I noticed is funny. So I got a ping saying "2 answers ..." for this post. But as +10k users will readily find out, there is only one answers.
I assumed that if one is quick enough to delete a post it gets ignored by the system. But now that pinging seems to be buggy and also, since I got notified for 2 answers, I thought I'd post on meta.
Here is a screenshot for when I got pinged for 2 answers when there only is one:
