css version tested with stylus:

    .score { display: none } /* stories and own comments */
    .pagetop { color: transparent !important; } /* hide karma top right (also hides username and logout) */
    #me, #logout { color: black } /* show username and logout */
    #hnmain > tbody > tr:nth-child(3) > td > form > table > tbody > tr:nth-child(3):not(.athing) { display: none } /* own profile */
    #hnmain > tbody > tr:nth-child(3) > td > table > tbody > tr:nth-child(3):not(.athing) { display: none } /* other user profile */

I don't think it could easily be truly hidden but a css experiment might be interesting.