The thing is that ~ is special shell magic. $home is an environment variable, and is consistently expanded as such.
Although, to my eyes, the most plan9-y way of implementing a home directory would be to have '/home' as your home directory no matter what, and have it default to a bind from /usr/$username.
btw why /usr? I get it that in unix legacy it started as the users folder, but won't this be confusing as hell for all people that have come to know it as unix system resources? Why not /users?
Because that is what it's called on plan9.
Ah, fair enough. I really only meant to cite the one example - since I found it so striking when I first saw it. (It had never occurred to me to use sed for head that way.)