Here's a good explanation of kerning taken from Powerline. This is what convinced me.
---UPDATE 10: Reader Jon-Erik Prichard adds what strikes me as an especially persuasive point:
[A]nother aspect of the type on [the August 18, 1973 memo] suggests, perhaps proves, forgery.
1. The type in the document is KERNED. Kerning is the typsetter's art of spacing various letters in such a manner that they are 'grouped' for better readability. Word processors do this automatically. NO TYPEWRITER CAN PHYSICALLY DO THIS.
To explain: the letter 'O' is curved on the outside. A letter such as 'T' has indented space under its cross bar. On a typewriter if one types an 'O' next to a 'T' then both letters remain separated by their physical space. When you type the same letters on a computer next to each other the are automatically 'kerned' or 'grouped' so that their individual spaces actually overlap. e. g., TO. As one can readily see the curvature of the 'O' nestles neatly under the cross bar of the 'T'. Two good kerning examples in the alleged memo are the word 'my' in the second line where 'm' and 'y' are neatly kerned and also the word 'not' in the fourth line where the 'o' and 't' overlap empty space. A typewriter doesn't 'know' what particular letter is next to another and can't make those types of aesthetic adjustments.
2. The kerning and proportional spacing in each of the lines of type track EXACTLY with 12 point Times Roman font on a six inch margin (left justified). Inother words, the sentences break just as they would on a computer and not as they would on a typewriter. Since the type on the memo is both proportionally spaced and kerned the lines of type break at certain instances (i.e., the last word in each line of the first paragraph are - 1. running, 2. regarding, 3. rating, 4. is, 5. either). If the memo was created on a typewriter the line breaks would be at different words (e. g., the word 'running' is at the absolute outside edge of the sentence and would probably not be on the first
line).
3. The sentences have a wide variance in their AMOUNT of kerning and proportional spacing. Notice how the first line of the first paragraph seems squished together and little hard to read but the last line of the first paragraph has wider more open spacing. Even the characters themselves are squished in the first line (as a computer does automatically) and more spread out on the last line where there is more room.
There's no way a typewriter could 'set' the type in this memo and even a good typesetter using a Linotype machine of the era would have to spend hours getting this effect.---
Your right about the kerning varying from line to line. This is definitely Word, the "squishing" is a function in Word, which really annoys me, because WordPerfect doesn't do it. WordPerfect is a much better program but everybody uses Word now.
NOTE TO DAMNOCRATS:
"To forge, don't use typewriter."