What happens if I jump with crew members teleported away on another ship? I've never dared try.
They die. Same when the ship is destroyed when they are still boarding it. I have tried it sadly. :(
(Comment inspired edits)
The game does warn you if you try to jump away before you gather your crew. But the game doesn't warn if you teleport crew unto a ship without life support.
Your crew is also gone when the enemy ship jumps away.