While waiting for a recent flight, I observed this aircraft with what appear to be rather worn turbine blades. Is this close to being a safety issue or is it purely cosmetic?
Yes, it is safe. Prior to every flight, ground technicians and one of the pilots will complete a pre-flight walk around of the aircraft, which includes checking the engines thoroughly. Any issues with the turbine blades would be noticed at this point and the flight would not depart.