Subject that ends with UTF-8, 85 or A0 e.g.:

[Kevin J. McCarthy]

On Wed, Aug 03, 2022 at 12:21:09PM +0900, Kenichi Asai wrote:
>asai at bigsur % cat test.c
>#include <stdio.h>
>#include <ctype.h>
>
>int main ()
>{
>  printf("%d\n", isspace(0xa0));
>  printf("%d\n", isspace(0x85));
>  printf("%d\n", isspace(0x0a));
>
>  return 0;
>}
[...]
>asai at bigsur % ./test
>0
>0
>1
>asai at bigsur %

Darn, that was my best guess.  After I sent the email, I even found some 
old bug reports that 0xa0 was considered "space" on MacOS 
(e.g. https://bugs.python.org/issue7072)

Still, perhaps there is something different about the way Mutt was built 
versus the quick compile.

Have you ever built Mutt yourself?  Would you be able to try, and try 
applying the attached patch to a recent release tarball?

-- 
Kevin J. McCarthy
GPG Fingerprint: 8975 A9B3 3AA3 7910 385C  5308 ADEF 7684 8031 6BDA
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