Mycroft has turned 221B Baker Street into a shrine, everything inside left like Sherlock had never left, and members of the “I Believe In Sherlock Holmes” campaign leave notes, cards, flowers, mementos at the door like offerings. They do the same at Sherlock’s grave, but 221B seems to be as iconic as the late detective. John reads each letter and note, overwhelmed by the outpouring of support and well wishes. He never knew his blog reached so many people; that Sherlock's death would be mourned and his reputation fought for by the masses.
He doesn’t keep the letters and notes, instead gathering them together every week or so and sending them off to Mycroft. He always receives a polite text after a couple of days, a simple, thank you.
It takes a month and a thousand more letters, comments, notes and cards before John can reply, You’re welcome.