If I don't hear from them in a week or two, I put a comment "awaiting response to email" in their coordination request and return it to them. Returned requests will expire in 3 months if no further action is taken and do not generate coordinator reminders.

In that case it is not so bad. However, my experience is that most users who do not understand the portal (and of course there are more of those in my country, because they have the language barrier in addition to the already complicated matter) and get a request returned to them (previously this was called rejected, now it is called returned) will always manage to click on the re-submit link. So the ball is again in my park, and when I don't play it back to them, I get the reminders. I have once got it returned 3 times this way.

Normally it is not a real problem when a requester does not come back after requesting additional information, because (here) the original request usually wasn't what they wanted anyway (we use the portal only for IPIP gateways).

Rob