Blink actually doesn't have any i-frames. At all. It's just people don't realize that you're not at the place they're shooting at anymore and that makes them mad. Yes, you can blink an invite amount of times in air. But it still undergoes the inner cool down. Blink is a teleport, not a jump. It procs off cool down, not resets at landing like jumps. And they won't lower weapon ready times with it because that'd be logical and bungie doesn't like that.