>I find the message reply style, in which the new message gets appended to the bottom of the messages, to be time-comsuming and inconvenient: the part I want to read is below the screen and I need to scroll it up. Wouldn't it make more sense to have the default reply be at the top of the message, so it could be quickly read?

This is the user's decision. He or she decide where to put their reply. Also, a reply might be divided in parts where it is within different sections of the previous message.

As for keeping a copy of the previous reply when replying, this is also a user's decision. The configuration is made in the user account configuration. This is something you control.

>Also, and I realize this is a bit more difficult, it would be a lot more useful if the enclosed "original" message included only that which was in the immediately preceding message. Of course, if the new stuff was at the top of the new message, this wouldn't make much different to me, other than the time to transmit the message (still an issue in web-based boards).

Again, refer to my reply on top.

>Also: the Next button works fine until the end of a branch is reached: but then you have to go back to the map to find the next sibling to the top of the branch you just worked through. I realize this is technically correct; but there should also be a Down button which becomes enabled in that circumstance, which move one down the tree to the next message, on whatever branch.

This one is in our todo list.

>It would be most useful if the Map could be visible at the same time as working through the messages. The system that Neon uses is very good in this regard; and also has very quick response times.

If you have a 2000*2000 monitor, then yes, it would be nice. But, if I add another frame to display the map, people will kill me. :)

As for the other system you just mentioned, they don't have all the options we have here so comparison can't be made directly.