Copying this over from the suggestions subforum (https://ludeon.com/forums/index.php?topic=46490.0), at the suggestion of another poster:
In my current game, I sent out a two man (plus elephant) caravan to trade with a nearby faction. One colonist was meant to be the negotiator, while the other was meant as the primary guard. The latter is missing an ear, and has nine Social, while the former is healthy and has ten Social. The game decided that the guard should be the negotiator, forcing me to play around with splitting the caravan in order to avoid the penalty for having an injured negotiator. The game even brought up this alert when I first initiated the trade:
(https://i.imgur.com/wMJuBnq.jpg)
However, there does not appear to be an easy way to follow the advice given by this pop-up. I would like to request the ability to do so. I've also linked a save, so anyone that wishes can look at this, and see if there's a way to do this already that I'm not seeing.
https://www.dropbox.com/s/2n5tp00y7beptdd/Set%20Caravan%20Negotiator_.7z?dl=0
Your one-eared guard has inspired trade with 30.74% trade price improvement.
The other guy has 15.00% trade price improvement.
You also have another guy back at the colony with inspired trade and 31.50% trade price improvement.
The health warning is a bit misleading in this case. Maybe it shouldn't show up, if the injured guy is the best trader in the caravan.
I modified the bug title to reflect the issue. This warning dialog should not appear on caravans (only on trading on the map), since the best negotiator is chosen automatically in caravans.
Fixed, thanks for reporting! ;)