Well yes, probably everyone on HN is computer-savvy enough that when they type some input into a general consumer application, they damn well mean what they sai

Well yes, probably everyone on HN is computer-savvy enough that when they type some input into a general consumer application, they damn well mean what they said, not what the application thinks they meant. I wonder if there's cases where this has degenerated into a game of "guess two-thirds of the average": your app starts out with a level of automatic input cleaning which is not enough to catch all the mistakes of the least savvy 1/3 of your users, is mildly helpful to the next 1/3, but annoys the top 1/3 enough that they switch to another product. Then the least savvy users are half of your userbase, so you lower the focus of your product to account for them ... (this assumes that the least savvy users don't know how to switch products, since if they knew that much they wouldn't belong in the "least savvy" category).