by MihaiBorobocea:

What does 'go version' print?
go1.3

What steps reproduce the problem?
package main

import "fmt"

func main() {
    fmt.Printf("(%5q)\n", "§") // (  "§")
    fmt.Printf("(%5q)\n", '§')   // ( '§')

    fmt.Printf("(%3s)\n", "§") // (  §)
    fmt.Printf("(%3c)\n", '§')   // ( §)
}

// Or run this same program at http://play.golang.org/p/UHE8wQK50u

What happened?
When printing a rune with %q or %c and specifying a width (for padding with spaces) the
width is counted in bytes. The program prints the rune U+00A7 which uses 2 bytes in
UTF-8. The lines with rune args produce a string shorter than the corresponding lines
with string args.

What should have happened instead?
The width should have been measured in runes, like it happens when printing a string.
Package fmt's doc says “Width and precision are measured in units of Unicode code
points”.

Am I misunderstanding how this is supposed to work? This seems too basic to have gone
unnoticed.
I've tried to find this in the code, and I'll attach an RFC diff in case my progress
saves you some time.