Dragonlord's comments made me review my test map more closely. He's right, putting multiple start points in one system
doesn't work. I thought it had because I only looked at my own starting system, and not the AIs'. (And had misremembered which worlds I'd marked in my start system, too) Not only doesn't it work, but the multiple start points will override the "Can't start in same system" setting in the Set-Up screen, as well.
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Cap'n Q
My first mod!
Hypermaze quadrant
The most merciful thing in the world, I think, is the inability of the
human mind to correlate all of its contents. We live on a placid
island of ignorance in the midst of black seas of infinity, and it was
not meant that we should go far. -- HP Lovecraft, "The Call of Cthulhu"