I only ever it did it full-scale on a FOWLR - worked very well. I did not worry about alk on a FOWLR.
It is too risky on a reef tank for me. I cannot risk driving the nitrate down to near-zero.
The benefit is that it can lower nitrate... not so much phosphate, but it can lower a bit. The most successful implementations monitor nearly every day and use organic carbon to keep their levels very low through massive export, but also massive import - ZEOVit is the most common example of this. In these tanks, there are tons of building blocks available to the animals, but the residual values are kept low. The people who do carbon dose on a reef keep their alk at NSW levels in the 6s.
Keep in mind that carbon dosing does not really do anything. You need to use a good skimmer to remove all the bacteria that you are growing from the tank. If you do not have a good skimmer, then some of this could be for naught since the bacteria just die and recontribute to the N cycle if you cannot remove them.
Without strict monitoring and control, you can grow too many bacteria which will outcompete the corals and algae for building blocks and they can suffer - this is quite common in the post-BRS video era of reef keeping where people put bio pellet reactors on their tanks when they were brand new when they had no excess of building blocks to remove. If you add too much too fast (overdose), then the bacteria will QUICKLY (and I mean quickly) multiply and use up all of the oxygen and suffocate your fish and inverts.
On my FOWLR, nitrate got up over 20, which stopped all coralline algae growth. I dosed sugar quite aggressively for a few months and got it down to about 1, then kept it there with a smaller dose. My only goal was to get the coralline growing again, which it did. I went really slow because I did not want to use up all of the oxygen.