Oh, boy, lots of confusion here.

Here's what I think, and I'm sure it's going to lead to more confusion, but here goes.

This board, indeed any device that attaches to the computer using a serial port, has to "reverse" the names of the pins and the nets attached to the micro.

In other words, the micro's transmit pin should be connected to the serial port connector's receive pin and that net should be called receive.

Likewise, the micro's receive pin should be connected to a net and connector pin called transmit.

This will go a long way towards simplifying the external cabling. No null-modem or gender-bender or custom cables required. All that's needed is a straight-through cable.

Sure, the schematic looks funny, but the nets and connector are labeled according to their system function.

-a