Is it bad to close furnace dampers in order to balance temperatures seasonally?
Yes, if you close too many dampers, you can overly restrict air flow which will burn out your furnace motor. However, what’s more likely is air flow will increase in the ducts/grills that have not been restricted. When this happens it could create a “whistling” noise because the ducts are too small for the amount of air being pushed down the duct. 

When we design heating/cooling systems, we try to balance the air flow so more air can go where there is greatest heat loss/gain. Partially closing one damper will cause more air to flow to other ducts/grilles. So, yes, you can adjust your houses temperature in various rooms by changing (opening/closing) dampers.