ah, how I am enjoying this gift! you've touched several lovely tender places, and made my heart glad for them.
Harry's instinct to walk in silence with Severus is very wise and beautiful; it creates an intimacy and a truthfulness for them that is maybe at the heart of what I love about Snarry. They are deeply wounded, and scarred by such enormous grief. So what better healing than to just BE present?
here are a few bits I loved: He can almost feel Snape draw in and stone himself. I love "stone" instead of "steel" - very apt, considering their relationship with the castle.
and Severus is good at duty. oh, yes. he is. I feel his weariness.
“I know you think this is wrong. I do, too. But maybe it’s the wrong things that are right sometimes. go, Harry!
I love the ending, too... it's a perfect balance of "we have no idea where this is going." and "I will love you forever." nicely done in a few words.