Hi,
Is it correct to say "the system has proved incapable of reform"? Or should one say "the system has proved to be incapable of reform"? Or maybe both phrases are wrong?
Both sound OK. However, I find the meaning here ambiguous. Do you mean the system is incapable of receiving the reform, or of performing the reform? eg
The public cannot reform the health system or The health system cannot reform the public (eg in their attitude to nutrition or exercise)
If the former, a clearer sentence would be the system has proved (to be)incapable of being reformed.
Best wishes, Clive