My response:
Just .02 cents worth from the peanut gallery.
It really doesn't matter if the Agent for Service tells anyone or not, and a "confidentiality agreement" in this regard is really worthless.
You see, a lawsuit is "public record" anyway. So, whether the Agent says anything really doesn't matter. An Agent, like anyone else, can talk about Public Records at any time they want, to whomever they want.
As a matter of fact, if I wanted to find out if a lawsuit was filed by, or against anyone, or any corporate entity, all I would have to do is go to the courthouse and look at the Registry of Actions, and then have the Clerk pull the file for me. The court file is not private, and the ensuing litigation certainly isn't private.
The presumption, and the fact is, that by the time the Agent for Service has received the Summons and Complaint, the action has already been filed in court, and is already in the "public record"
So, anyone can get this info regardless of whether the Agent says anything. And, if the Agent does mention it, he's not "telling tales out of school" by doing so.
Summary: You can't "gag" someone from discussing public records - - unless you're a judge ordering the same.
IAAL