I don't know what you mean by "reviewer comments for a given change set".
It sounds like you might mean the change set 'comment', which is actually the author's comment, and not from a reviewer. It you do want the change set comment, then it looks like you have that information in the data fetched. It would be under the "comment" element (and thus it is "Updated the  getAttributeEnumLiteral()" in this case).

If you want 'reviewer' comments it sounds like you might want to check-out the Code Review feature. In particular, the CLI command which lets you generate report based containing various Code Review metrics. Here is a summary of the Code Review tool if you are not familiar with it:

In Rational Team Concert 6.0.1 we have introduced a new Code Review feature. Code review is integrated with RTC work items and Jazz SCM to provide developers with a seamless, low overhead work flow that is simple to use and is a natural extension to their daily activities. There isn’t a separate server installation, additional licensing fees or other costs associated with using RTC code review. Enabling code review for your projects is simple and takes only a few minutes to set up.

Reviewers can annotate specific lines of code, which helps developers quickly see and fix issues. Issues (or findings) can be marked as must-fix and the reviewer can accept or reject the changes. When preconditions are enabled, a code review cannot be approved if must-fix issues have not been resolved to everyone’s satisfaction.

Developers don’t have to worry about the intricacies of issue management because this is handled for them. Each issue has its own discussion thread and events are logged as the review progresses. Whenever an issue is updated, a new issue raised, or new code changes are added to the review, the events are logged so that you have a complete history of the review life-cycle. Because code reviews are iterative and can include code changes during the review cycle, any annotations on lines of code (issue markers) are automatically re-positioned and visual cues are provided to the reviewer so that they can easily see what has changed since they last looked at the code or since they last reviewed issues.

Team collaboration is accelerated through real-time notification of pending reviews, issues, and fixes. This is becoming more and more important as the number of globally distributed development teams increase. In fact, with the RTC SCM development team spread across three different time zones, it is common for them to have code changes that were written in one time zone reviewed by team members in another time zone.

Code review enables auditing for compliance. Issue status at delivery, approval information, the event logs, and other information captured during the review can be used for a variety of metrics and reporting requirements.

Since the introduction of code review in 6.0.1 more features have been added. Reviewers can inspect intermediate before and after file states which is useful in advanced SCM workflows encountered when multiple developers are working on a common code base. We have added the ability to filter issues on the navigator pane on the left, and various usability enhancements have been added.

The ability to extract work items is useful when an issue needs to be addressed but shouldn’t prevent delivery of the current code changes. The extracted work item captures the required work and will have its own code review cycle.