Is my carbon fork steerer tube damaged by overtightened stem bolts
In practical terms, it's impossible to tell for sure in a case like this. It's probably fine, but there's no way of knowing absolutely via visual inspection.

The surface indentations from the stem windows do occur naturally even with consistently correct torque on the fasteners. They're pretty normal to see.

It would be a good idea to get it as clean as possible so it can inspected closely for cracks or delamination. If you find any of that, it's toast.