DC++ incompatibility

The background for this mail is the problem described in (at least) two 
threads in the forum, namely:
http://dcgui.berlios.de/forum/viewtopic.php?t=2363
and
http://dcgui.berlios.de/forum/viewtopic.php?t=2538

I've posted using the name SuperTommy.

The function CDownloadManager::DM_TransferCallBack() in the file 
"cdownloadmanager.cpp" (line 3785 onwards, from "case DC_MESSAGE_KEY:") 
contains some code where the hierarchy of if's looks like this pseudo-code:

01: if ( Transfer->GetDstDirection() == Transfer->GetSrcDirection() )
02: {
03:     if ( Transfer->GetDstLevel() < Transfer->GetSrcLevel() )
04:     {
05:         if ( Transfer->GetSrcDirection() == edDOWNLOAD )
06:         {
07:             <change DstDirection to edUPLOAD>
08:         }
09:         else if ( Transfer->GetSrcDirection() == edUPLOAD )
10:         {
11:             <change DstDirection to edDOWNLOAD>
12:         }
13:     }
14:     else if ( Transfer->GetDstLevel() > Transfer->GetSrcLevel() )
15:     {
16:         if ( Transfer->GetSrcDirection() == edDOWNLOAD )
17:         {
18:             <change SrcDirection to edUPLOAD>
19:         }
20:         else if ( (Transfer->GetSrcDirection() == edUPLOAD) && 
(Transfer->GetDstDirection() == edUPLOAD) )
21:         {
22:             <output a warning>
23:         }
24:         else
25:         {
26:             <output a warning>
27:         }
28:     }
29: }
30: else
31: {
32:     bdirec = TRUE;
33: }

Question 1: Why is both SrcDirection and DstDirection checked on line 20 
when we've already established that they are the same in line 1? If 
there is a reason, why is only SrcDirection checked on line 9. This will 
of course not create any problems, but it makes the code look 
asymmetrical and difficult to understand for people like me, who has no 
previous familiarity with it.

Question 2: This is really my most important question; Why do we not try 
to change SrcDirection in line 22?

Question 3: Why is there an else on line 24 and not after line 12 (not 
very important, but I'm still looking for that symmetry)?

Question 4: What does SrcDirection and DstDirection do anyway? It looks 
to me like they need do be different, right? One side of the 
communication should upload while the other downloads, is that it?

best regards
Tommy