[Users] Interpretation of ~header ...

[RW]

In searches I would expect that in 

    ~header foo matchcase bar 

the ~ means the logical complement of the header test. And it is until
one tests on headers that occur more than once in the same email. In
this case:

    header received matchcase bar

means true if any received header matches bar but
   
   ~header received matchcase bar 

seems to be true if any received header doesn't contain bar (rather
than the complement, which would be: no received header contain bar).

IMO this is not only perverse, but close to useless for practical
filtering.