11 had's
 

[CODE]John where Jane had had had had had had had had had had had a better impression on the teacher[/CODE]

Unfortunately, in the above text, all the non-letter signs have been lost. You know, the !"§$%&/()=?`*'_.,-stuff. Please fill them in, but no new letters nor words, and use the spoiler-environment. H.

[SPOILER]
John, where Jane had had "had had", had had "had". "had had" had had a better impression on the teacher.

or, reversing John and Jane,

John, where Jane had had "had", had had "had had". "had had" had had a better impression on the teacher.

or, if you will allow me to capitalize one "h",

John, where Jane had had "had", had had "had had". Had "had had" had a better impression on the teacher?
[/SPOILER]

Fast. Had you [SPOILER] had heard the "had had"-[/SPOILER] solution before, or did you find it all alone?

I generated the solution based on experience parsing sentences many decades ago when I did Linguistics Research. I have also seen other puzzles that are solved in a similar manner, but not involving just one word.

I first heard this same puzzle many, many years ago.
But Wacky saw it first.

Recently I heard a longer series of repeated words about bison from a city in New York bullying other such bison. I found the buffalo sentence more contorted, though, while this classic "had" sentence seems straight forward.

[quote=wblipp;116277]Recently I heard a longer series of repeated words about bison from a city in New York bullying other such bison. I found the buffalo sentence more contorted, though, while this classic "had" sentence seems straight forward.[/quote]
[URL]http://en.wikipedia.org/wiki/Buffalo_buffalo_Buffalo_buffalo_buffalo_buffalo_Buffalo_buffalo[/URL]
"Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" = "Buffalo bison whom other Buffalo bison bully themselves bully Buffalo bison" = "Buffalo[sup]c[/sup] buffalo[sup]a[/sup] Buffalo[sup]c[/sup] buffalo[sup]a[/sup] buffalo[sup]v[/sup] buffalo[sup]v[/sup] Buffalo[sup]c[/sup] buffalo[sup]a[/sup]." (with c for the city "Buffalo", a for the animal "buffalo", and v for the rarely-used verb "buffalo", meaning to bully, or intimidate)

Yes. Contrived, and the word doesn't even occur consecutively.

8 buffalo's in a row, a play on different meanings of the same word again, similar to the "all prime numbers are odd" puzzle. Curious how the English language allows for such interesting occurrences.