大概看了一下,题目中最主要的逻辑错误是, only about 2 percent of customers have complained, indicating that an average of 98 people out of 100 are happy with the change. 没有抱怨就代表高兴吗?
many servers have reported that a number of customers who ask for butter do not complain when they are given margarine instead. Clearly, either these customers do not distinguish butter from margarine or they use the term ‘butter’ to refer to either butter or margarine.
典型either...or选择,事实上很可能有其它解释。可惜作者给出的解释有点不靠谱,margarine在欧美算不上a complex noun, 男女老少都知道。
除以上两点之外,其余是比较次要的技术问题,比如 a number of, 因此建议作者将主体第二和第三段交换一下。