Many federal workers who reponded to our April 17 poll did a lot more than fill out a ballot and send it in.

At least 400 of 18,000 letters we have opened and counted so far contained comments from civil servants who are not very civil where President Reagan's personnel reforms are concerned.

The president wants to change the federal retirement law so that workers must stay on the job 10 years longer to get full benefits.

Employes can now retire after 30 years service (at age 55) on an annuity equal to about 56 percent of salary. He also wants feds to shoulder more of the cost of the retirement system, by increasing their contributions (now 7 percent of gross salary) to 11 percent.

A pending rules change sponsored by the administration would consider performance rather than seniority when picking who gets within-grade pay raises, or who gets laid off.

This is what people are saying:

* "It is criminal to change an important rule for employes with 10 or more years of service who were expecting to retire at 55 . . . . "

* " . . . Carter was an angel compared to Reagan. My only hope is that Reagan ends up in an old age home being taken care of by a RIFfed nurse. He deserves the cold hands and square needles."

* "My complaint is not with requiring new government employes to work to 65 . . . . However, many of us entered government service at an early age under an implied contract . . . . I have planned my entire life to retire from government service at age 55. The fact that the government has mismanaged the retirement fund is not my fault anymore than it was the fault of my grandfather and my great uncle that their union cheated them out of much of their retirement due to mismanagement . . . . "

* "Your first poll question misses the point--of course it is fair to have federal workers work until 65, or 67, or 70, whatever--as long as that is the understanding at the start. It is not fair to let people work for 20 years then tell them they have to plan on working 10 more years than they expected."

* "Unqualified answers to your questions? You couldn't be serious! First consider the question 'regardless of how it affects you personally do you think it is fair to make government workers work until age 65?' How objectively can I, a 52-year-old with 32 years service, be expected to reply? Could I consider it anything but unfair to propose extending the retirement age 10 years beyond that firmly established at the time of my entry into government service?"

* "Asking what's 'fair' strikes me as a rather messy way of approaching an issue as emotional as the federal retirement system. What bothers me is the widespread misconceptions and ignorance among feds as to the true cost of the present system. This is not surprising since most of my colleagues with over 20 years service take the position that they have a 'contract' with Uncle Sugar that entitles them to be supported for life at essentially the same standard of living as they had while working if they simply hang in there until they are 55 . . . . "

* "These questions are not yes or no. Times and conditions keep changing. Government service is not what it was 25 years ago. It is not fair to senior employes to change the system to entrap them. After 25 years a person has too much invested to leave, plus his age is against him. Your questions are not fair!"