[imp] Reply to encrypted message doesn't include quoted original message

[vuser1 at test123.ru]

So I continue Horde/IMP deployment. I am impressed, very good email 
solution if you are not lazy to read config files and modify them 
according to your needs. Now the question:

When I reply to encryted message, instead of original message IMP shows:
    [No message body text]
Reply to normal or signed message shows original email as follows:
   Quoting <...>

But when I *forward* encrypted message, IMP shows text of original email 
- as expected. Is it a feature or bug? Why I can't reply with quoting, 
but still can forward?