Anything that restricts the flow of dangerous flue gases out of the stove could potentially be a bad thing, so all factory-installed dampers should still leave enough room in the flue to maintain a reasonable updraft. Theoretically, it will then be impossible to close it completely. Under normal operating conditions, a damper should never be required, and for safety reasons, flue dampers should only be installed when a flue draught problem has been identified.
While a good updraft is essential to the safe operation of your stove, too much chimney draught can limit your control over the rate of fuel combustion and your fuel economy, requiring you to reload your stove more frequently. Much of the excess heat generated will also quickly go up the chimney. In addition, you will not be able to turn the stove down when it gets too hot or when you want to put the stove to sleep.
Our recommendation is not to install a flue damper without first consulting a chimney sweep, installer, or other approved competent person. They will be able to carry out the appropriate tests, including a flue draught pressure test, to determine if there are any other problems that may be causing the lack of control or excessive fuel consumption.