Steps to reproduce:

Launch `emacs -Q`, paste these four lines on a buffer

aaaaaaaaa'aaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaa'aaaaaaaaaaaaaaaaaaa'aaaaaaaaaa
aaaaaaaaa’aaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaa’aaaaaaaaaaaaaaaaaaa’aaaaaaaaaa

nnnnnnnnn'nnnnnnnnnnnnnnnnnnnnnnnnnnnn nnnn'nnnnnnnnnnnnnnnnnnn'nnnnnnnnnn
nnnnnnnnn’nnnnnnnnnnnnnnnnnnnnnnnnnnnn nnnn’nnnnnnnnnnnnnnnnnnn’nnnnnnnnnn

Search for the first one with char folding enabled. In my system Emacs
doesn’t match the second line. It matches after I hit ‘C-M-d’ to
delete the last character from the search query.

If you search with char folding enabled for the third line then it
does match the fourth, even though the third and the fourth lines are
just copies of the first two with the a’s replaced by n’s.

All the best,
Andrea


In GNU Emacs 27.2 (build 1, x86_64-redhat-linux-gnu, GTK+ Version 3.24.30,
cairo version 1.17.4)
 of 2021-08-07 built on buildvm-x86-29.iad2.fedoraproject.org
Windowing system distributor 'The X.Org Foundation', version 11.0.12101003
System Description: Fedora 34 (Workstation Edition)

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list... [2 times]

Configured using:
 'configure --build=x86_64-redhat-linux-gnu
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Major mode: Lisp Interaction

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Load-path shadows:
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Memory information:
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