Snape not only allowed the touch, he inclined his head in a nod of greeting. "And you," he murmured quietly.
He was silent for a long moment, just enjoying Lily's supportive presence. He drew a deep, slightly unsteady breath, released it in a sigh. "You know what the worst of it all is?" he murmured eventually, "Not that the fucker killed him. It's that he died like that, after slithering out of trap after trap." It's said admiringly, as one Slytherin would say of another.
The absolute worst of it, Snape continued the thought silently, is that Riddle will have used his murder. Not just to stage his idiotic tableau, but to make a Horcrux!