So I had a child seat installed on the driver's rear seat in my sedan for about 8 months; there is a strap that runs from the seat, to the anchor behind the headrest. I had cranked it down pretty tight, and it indented the foam pretty good.
In the interest in reclaiming my legroom I moved the seat to the passenger side rear

Does anyone have experience with this or know how resilient the foam is? It's crazy cold here lately so the foam/leather is a bit stiff.

Is there any good solution to preventing this from happening on the other side?

 

it should come back to original or close to, when there is enough heat to do so. It won't happen over night though. Both the leather and foam should eventually rebound. If the cover was off, I would suggest using steam on the foam but since it is not heat is about the only thing that will work. We do use steam on the leather covers we make.
To prevent this from happening on the other side, place something under the cheild seat to help spread out the load. You will probably still have some stretching of the leather but it will help minimize it.

 

for the record, the headrest has SLOWLY been coming back to normal. not quite there yet, but soon, maybe warm weather will help. Should've taken photos of BEFORE so I could do AFTER

 

followup, we're at about 99% to normal on the headrest. I'd bet if I massaged the leather a bit it would be unnoticeable.

I am REALLY surprised it came back from the state it was in, hopefully this post helps someone else in the same situation. If you are planning on selling your car take the child seat out 6 months prior!