What do you think of Violet's father? Does she have a good reason to hide him from her friends? Is his plan to save language a reasonable one?

You have too many questions here. Generally, Violet's father is an old school eccentric. He longs for the days when language had meaning. He longs for the depth of Shakespeare and Chaucer instead of the technology shorthand language that is used in the book. Some people might consider Violet's father to be crazy or rebellious.