[Users] How does Status field in message summary work?

[Milan Obuch]

Hi,

as I recently does some mail archive cleaning I moved quite a number of
message to another folder. Link to reply message get lost when moved.
More precise:

Originally I had some messages in INBOX, when I replied to it, reply
message was stored into Sent folder. In summary view, there was a small
square with red arrow pointing up/left in Status field after reply was
sent. Clicking this icon finds this message.

It looks like it is implemented as quick search with Extended search,
expression inreplyto matchcase "<message-id>". OK.

However, reply message is not found if moved out from Sent folder or,
as I just discovered as I am writing this, it was not stored in Sent
folder, but elsewhere. So is Sent folder hard coded in search of reply
message?

Regards,
Milan