Not exactly. Any account that you add game time to (which is required to post outside of the Support-based forums) can not be deleted. Only starter accounts that have never had game time can be deleted.
That said, yes, there are people who will always be sad enough to try and continue communicating with someone who clearly no longer wishes to be contacted. In many cases, as we’ve seen in this thread and in others like it, the person attempting to game the system almost always wants to blame their victim.
However, the fact that there are sad individuals out there who can’t understand simple boundaries, is exactly ‘why’ we need a system to easily ignore them. Moving to the same system the rest of the forums use (b-tags) is likely the most accessible option for Blizz to have Discorse (the forum software that they use) program for them as it’s already something that they’ve done.