How to write about something negative without negativity

Take a look at this letter of recommendation below.

To Whom It May Concern:

C has been an intern at XX XXXX XXX Retirement Community since September of 2011.

C has a genuine interest in helping people. She has had an interest in the elder population since she was younger as her mother is a nurse and has worked with the XXX Communities for many years. C also shows an interest in social work and aspects related to social work.

C has been exposed to different aspects of elder social work including, but not limited to: interviewing skills, cognitive assessments, clinical documentation, and Medicare rules and regulations.

As part of her current responsibilities at XX XXX, she is working with the Assisted Living staff to create a weekly group for Residents to discuss topics/articles of her choosing. She is also currently working on Life Reviews for two Residents (one long term care Resident and an Assisted Living Resident).

I would recommend that C continue her social work training at the University Of XXX School Of Social Work and complete two full internships to continue her training in the field of social work.

In this letter, the most important things the writer is trying to say are left unsaid.

A colleague of mine submitted this letter to the university program directors for her intern. Her goal was to list the assignments and responsibilities of her intern without suggesting that the intern had any competency or skill. She hoped to convey, by leaving out any positive words, that the intern is awful.

When you manage staff or interns, performance reviews for poor performance can be a challenge. It’s important to be honest and clear without coming across like you have a personal grudge.

How do you handle these situations? Are you completely blunt about failures and shortcomings? Or do you strive  to avoid sounding like a big whiner even though you must write about something that’s going just terribly?