I think writing and reading are two different forms of communication.
When writing, the author gives the reader a single-voiced, one-way experience. As a storyteller, the author provides hours of her/his view of the world and creative inspiration. They do it without ever knowing who their reader will be - a shout into the darkness, a gift to the cosmos, a prayer to be heard.
The reader receives this communication, and then chooses whether to attempt to engage the author in a conversation, or not. It used to be the author's prerogative to refuse to talk to readers, but that time is over. Modern authors that don't engage with their readers risk marginalization, or worse, revengeful reviews.
Personally, I think every author should cherish communications from their readers, and answer their questions in good faith. I also think readers should feel free to respond to the author's body of work, but treat the relationship in the same way a purchaser of a painting would one with the artist. Asking about inspiration, technique, subject matter, any manner of things pertaining to the author's work is fair and encouraged, but it's crossing a line to ask for personal information, or to presume on a friendship that doesn't exist. One might develop over time, but in the beginning the author knows nothing about the reader, while the reader has already gathered an impression of the author from the books they've written.
It's easy for a reader to feel close to an author long before the feeling might be reciprocated. Please, gentle readers, approach authors you wish to befriend with a quiet understanding that they are most likely loners by nature. They have to be or no books would ever get written. And it's their speculative introspection that makes most authors nervous about new relationships.