I think having a reviewer that knows the codes and can understand the calcs is a good thing. Otherwise it's just a rubber stamp from someone who has little idea what they're looking at. Annoying when they take issue with my project because I can't brush them off as someone who doesn't know what they're talking about, but good overall.
The whole process works best when it's noncombative. Reviewer needs to make sure that they're confident the design PE knows what he or she is doing and is following the building code (if not to the letter, then at least in spirit for judgement calls). Determining whose call it is when there's an impasse is a difficult issue and not always driven purely by engineering (see below). As a design engineer, my feeling is that ties should go to the stamping PE. The stamping PE is the one putting their career and financial wellbeing on the line with every design they stamp. Generally PEs in planning/building department are protected from lawsuits. That said, if the reviewer is absolutely certain the design engineer is incorrect then they need to hold firm. We've all seen (in our opinion) bad designs with a stamp on it.
Also design PE needs to keep in mind that it may be easier in some cases to just do what the reviewer is asking. I had this issue on a high rise peer review recently. I disagreed with the reviewer on an item where they wanted to add a fair amount of ties to a couple of walls. The code committee member we had retained to help keep us in line also disagreed with the reviewer. But the reviewer was pretty adamant about this item. As fate would have it, it was the last item remaining in our review process, everything else was resolved. We talked with the owner's rep and explained the situation. We helped estimate the material cost of what the reviewer wanted to add, and made it clear we didn't think it was required but that including would at worst have no impact and at best be a betterment. In the end, the owner decided to just eat the cost and add the ties. If it means the difference between being done now/soon and continuing the process for weeks/months, then it may make more sense to spend the material and save the time.