SCENARIO 1: 
----------------- 
 
Suppose you are taking part in a discussion in a thread. You first 
read all replies, thus marking the messages read.  Then you decide to 
reply to those messages which were replies to your posts.  So, you 
need to know whether someone has replied to your message. To ANY message 
written from you. 
 
In other words, you must visually locate all the posts: 
 
1. that are replies to your posts; 
2. to which you have not yet replied. 
 
 
This is difficult in pan, and easy in Agent, as you can see below: 
 
Pan: 
 
Hello! How are you! This is the title.                   me 
   Re: Hello! How are you! This is the title.            jack 
      Re: Hello! How are you! This is the title.         frank 
   Re: Hello! How are you! This is the title.            frank 
      Re: Hello! How are you! This is the title.         john 
      Re: Hello! How are you! This is the title.         me 
         Re: Hello! How are you! This is the title.      jack 
            Re: Hello! How are you! This is the title.   jack 
            Re: Hello! How are you! This is the title.   jack  
         Re: Hello! How are you! This is the title.      frank    
   Re: Hello! How are you! This is the title.            john 
 
Agent: 
 
Hello! How are you! This is the title.                   me 
   jack 
      frank 
   frank 
      john 
      me 
         jack 
            jack 
            jack  
         frank   
   john 
 
 
Of course Agent is better for that purpose: in agent, what  
you do is visually scan the thread for the pattern: 
 
   your-name 
        ... 
            ... 
                 ... 
        someone-else-s-name 
           ... (not your-name) 
 
(notice the indentation). 
 
In pan you can't do that at a glance,  
because the names are equally aligned. 
 
SCENARIO 2: 
 
you want to locate frank's reply to your post. 
 
the problem is the same and I won't illustrate it again. 
 
------ 
THEORY: 
 
The problem in Pan is that the topic rarely changes, nevertheless it 
is given a big importance (by means of indentation), whereas the 
author is more important, but it is given minor importance by means of 
no indentation. 
 
Let me repeat: "the author is more important that the subject", because the author 
often changes and the subject almost never does (and even when it does, this 
change is irrelevant and is reflected in the body). 
 
So, if only one between the author and the subject must be indented, that should 
be the author. 
 
---- 
 
SECOND SUGGESTION. 
 
So far, I've suggested to give authors a better emphasis with respect to subjects. 
Now I'm going to suggest to remove subject almost entirely (i.e. as agent does, 
see above examples). 
 
This is because redundant info is annoying. The topic of replies is totally 
irrelevant, even when it changes---and if you don't think so you can still read it  
inside the message when it (rarely) changes. 
 
Or you could do like Xnews: just display the subject when it changes. 
 
My subject bla bla ba                             myself 
    john 
       frank 
 
    jack 
       myself 
           You are so stupid (was: ...)           jack 
              frank 
           jack 
 
 
But please, remove reduntant subjects, because they drag the attention away from 
important things.