I'm editing a PhD dissertation and found that the author reused sections of his paper such as Methodology in Chapter 1 and Chapter 4. It seems that his Chapter 1 is a synthesis of the succeeding 3 chapters, so parts from those chapters were just repeated in Chapter 1. Is this acceptable?
It likely depends on the field, and the norms at your particular institution. It is certainly common for dissertations to summarize portions of themselves (they are often 200-800+ pages, summaries are nice).
Based on your question, I wonder if you are concerned about self-plagiarism. I don't believe that this would rise to the level of self-plagiarism, as you are talking about a single document that is (usually) copyrighted by the author and will be published as a single document.
However, in my opinion, that is sloppy work. A good summary should be written to be concise and information dense, rather than an exact replication of other parts of the document. Instead of replicating, it may make sense for the student to reference the other chapters. For example "See Chapter III, Section [insert section] for a summary of [insert what is being summarized]".
Dissertations are already long enough, I don't believe that students need to draw them out through needless repetition.
If the student has copied verbatim from the Chapter 1, then it is not usual and should not be ignored.
If he/she has used the same methodology in a different way to solve a different flavor of problem, then you should look the methodology once more before commenting (just to make sure).
In such a case, the student should use like the following statements without rewriting the same section.
The methodology employed to solve the problem X in this chapter closely follows the methodology which has already been described in Chapter 1 (may be he/she could give a hyperlink, for online purpose).