Can cold-brew coffee be heated? Why? Apparently keeping coffee hot and reheating it both lead to bad flavors:

How can I reheat coffee without imparting bad flavor?

Why does coffee taste awful after reheating it in a microwave oven?

However, can you cold-brew coffee and then heat it (microwave or other) without ruining the flavors?  If so, why?
Yes, you can.

In fact, this is a specific technique known as a "coffee toddy" which is a good way to take liquid coffee camping with you if you don't want to take brewing equipment.  Some people even prefer coffee made this way to other methods of brewing.