This should probably be "test if arguments"

This was also filed as a PR here: https://github.com/S3-working-group/s3-practical-guide/pull/31

Double comma should be single

This should probably be "but also"

The closing bracket is included in the bold which is inconsistent with the following paragraphs. The ** in markdown should be moved left of the bracket. There is a PR for this (and a couple of other typo fixes) already here: https://github.com/S3-working-group/s3-practical-guide/pull/31