Would prefer sending to 2587623823894059467[check digits] when I need to enter the entire address and unable to use aliases, and sending to John, or John276, or any other alias of my choice when I can. If I use alias, I do so accepting the consequences of mistyping. I think most regular folks would also feel like this.
726 in John726 is the CRC-sum.
Yeah, I know what you mean. And the client can (have the option of) enforcing only CRC correct aliases. If I'm forced to choose only between 1) and 2) (like a bad democracy

), I would choose 2). But ideally, I want to choose 3), the way I described. And client is the way to go for 3).
EDIT: I like jl's idea! Computers should always be assisting humans with info like this.