Respond to code review feedback
Respond to code review feedback

- Remove reads of indirect `Place`s
- Add comments explaining what the algorithm does

aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust