Thanks for checking.  That actual was with `-f`, and I've now
double-checked all cases (setting only histignorespace, only histnostore,
etc) and still see the same behavior, even after upgrading to 5.0.7.

Couple more examples:

    % zshaddhistory() { return 1 }
    % preexec() { echo $1 }
    % true
    true

    % setopt histignorespace
    % alias test=' true'
    % preexec() { echo "$1,$2" }
    test,true

I feel like I should provide some more information, but I'm not sure what
would be helpful.