when $duplicate_threads='no' and no threads sorting mode duplicates can't be found

[m.m]

I able to use the ~= pattern search only when $duplicate_threads=yes and sorting mode by threads. The first condition seems to be a bug, according to the documentation, while the second seems like a 'known fact', although not documented.

It is a bug because when $duplicate_threads is 'no' duplicate messages couldn't be found.

I checked this on a maildir folder.

(I checked on .1.5.11, and 1.5.16 (last available version))