Just a couple of quick comments on this great thread...
NEVER write on a stamp, its selvage, or an album page

I do confess that I have removed selvage to make my album pages more symmetrical. Obviously, with most of the examples you've shown above, the selvage contributes to the design, value, or identification of the stamp. I wouldn't remove those either.
But for an ordinary, modern stamp that will never be rare or above minimum catalog value...