There was a period last summer when my 25-year-old sister, Willa, decided to start communicating with me through comments on the rapper Drake’s Instagram feed. Sometimes it would just be to say hi; other times to inform me of her plans for the weekend, or to relay an amusing anecdote. Once or twice, we carried on full back-and-forth conversations. I didn’t think much of it at the time. Sure, it seemed a little strange that she wouldn’t just text me, but I figured it was just some Millennial Thing I didn’t understand.