Definitely 2 schools of thought.
(a) they left and came back. a message to others that the grass isn't greener; and
(b) they left and we cannot show weakness to our current group. There is no safety net if you leave.
Thinking back over my career, I was someone who thought/practiced bringing people back made a powerful statement about "grass isn't greener" to current employees. In truth, it never worked out long term. Way too many malcontents in this world.
Bottom-line, always do what is best for the organization. No hard rule. Assess on a case by case basis. Poach clients, talk smack, show disrespect...bridge burned. Make a personal decision but act professionally...no bridge burned.
I will say, it also takes a little self-reflection. As the "organization", maybe part of the transfer is your fault. Own it when necessary.