The 'Block All Whispers' feature is a good one, but it does have one tiny flaw.

If a person whispers you again, after receiving the 'you do not meet the requirements' message, it is not blocked on account of the fact you auto-whispered them. As you know - because you did write it - if you whisper someone, it doesn't block further communication from them.

I've had to set 'Others' to Level 111 in order to truly block all attempts - usually by arrogant elitist swine calling me a chicken for not dueling them - to whisper me.