I recognize you already have a more official response about your proposal here, but I feel it needs to be said given my past experiences...
In all my time, I have never heard of this term you call "sniping". It's not really an accurate way of describing what you desire.
But if it were accurate... take cover (block) and move out of range (delete) to not have to deal with the "sniping". If you want to "counter snipe", prepare for a long drawn out fight since there's no headshot instakills in this 1v1 sniping arena (private messages). A slowly rising cover would not ultimately change anything (your suggestions). All it would do is prolong the fight further. The ammunition of this sniping arena (messages) can't penetrate to anywhere it would physically incapacitate the opposition to actually settle things. If one side in the arena wishes to take a pot shot and instantly take cover, that's ultimately the end result if both sides engage.
Outside of that analogy, you realize you're posting in a public forum right?
Thus, the person who you clearly want to get back at in some form, if they cared to see your response would be RELISHING in your behavior. Especially with how you typed out this suggestion, stating this as a clear response to being disturbed. Which is very likely the EXACT response a person who sends an inflammatory message and blocked you afterward wants you to be feeling.
I'm not going to assume anything about people, but you need to realize how much your own behavior feeds the exact thing you propose fixing. The solution to which is in your control already: you blocking and deleting the offending user/message. As you've been told multiple times, some more direct than others.
Now to be clear, I'm not saying any of this with negative intent or malice. I'm not sure how to truly convey that through the medium of English text.
My intent is to make you aware of a potential trap you fell for. This is in regards to a person aiming to gain pleasure out of other people's displayed negative emotions. All your responses here indicate that you do not understand that potential.