I found two examples of this kind in Harry Potter so far and in both cases, the speaker is Mr. Weasley and the listener is Harry. Does it add some nuance? Is it his habit of saying?
(In a lift of the Ministry of Magic building. They reach their story.)
”This is us, Harry,” said Mr. Weasley, and they followed the witch out of the lift into a corridor lined with doors. “My office is on the other side of the floor.” (Harry Potter 5 [US Version]: p.130-131) [Bold font is mine]
(They are looking for the camp site they booked in advance.)
”Always the same,” said Mr. Weasley, smiling. “We can’t resist showing off when we get together. Ah, here we are, look, this is us.” They had reached the very edge of the wood at the top of the field, (Harry Potter 4 [US Version]: p.79) [Bold font is mine]