We've been through this before bob and you are still confused...
"The word kern is a cognate of corner. In the days when all type was cast metal, a corner was notched to a consistent height on one or both sides of a letter-piece. Such notched pieces were only set against one another, not against unnotched ones, which had straight sides. The corner allowed for a character's features to reach into the area normally taken up by the next character, for example the top bar of the T, or the right diagonal stroke of the V to hang over the bottom left corner of an A."
True, with some fonts in some faces. Almost always in larger point sizes of Roman faces and more of a rarity than common place, I can't recall when last I saw a type drawer with notched characters. Other than some with extreme extensions of such elements as the tail on a 'Q', the leg of an 'R', the descender on a 'g', etc.
Those decorative items notwithstanding, I recall the notching accommodated serifs top and bottom sharing a bit of real estate, it did not allow slanted verticals to overlap, as in the ever popular "AV" example. Nor did it allow lower case characters to slide under or over right slanted verticals of upper-case characters.
In the site from which you copied and pasted your information [shame on you for not including a proper attribution],
http://www.bookrags.com/wiki/Kerning
look down at the three examples of the word '
WAR' Note that the middle example merely sharing serif space is probably the most visually pleasing. The top is too wide and the bottom too close in. You could get away with using either the top or the second examples, but the bottom is bad typography. Not only is it bad typography, it looks bizarre if not awful.
In general, there is no typographical objection to some characters sharing horizontal serif space. Serifs can be just another flavor of extension. Contrariwise and again in general, there is an objection to having the bodies of two characters sharing the same space.