I have a 32 Inch TV i play on and TXT is fine, my old man has a 40 Inch TV and his scales fine. Never heard of an issue whilst using a TV as a Monitor.
But maybe, just maybe 42 inch doesnt scale well, try a monitor to see is the scaling/sharpness of the txt improves.
Be nice to know if this was the culprit. Was looking at getting a 42 Inch TV (as a monitor) myself sortly.