Unfortunately, there is no automated system for requesting that case can be closed.
Anyone is free to send me a list of their cases that they feel can now be closed. I love closing cases. 
paul@xojo.com
And if you have (or see) a case that is in the “Reviewed” status for what you feel is too long, go ahead an add more comments or examples to it that might help make it easier to reproduce.
Am I to assume, then, that by adding a new comment, the issue isn’t triggered internally to be reviewed again? i.e. to the example issue, I added a comment “This can be closed.” I would have suspected that someone at Xojo would have gotten an email or something stating that an issue was in your court (i.e. you guys were the last one to alter/comment on it) and now a customer has updated the issue. Thus, you guys look at it and see “This issue can be closed.” ??
Only staff that are attached to the case in some way are notified (commented on it, assignments, marked as favorite, etc.), so it could fall through the cracks.
When are staff associated with an issue? For example, if an issue is “Reviewed” does that mean a staff person is associated with the issue and they will be notified when a customer comments on the case or is it, gulp, possible to have a customer comment on a case and no one be notified?
I don’t exactly know. I don’t believe “Reviewed” cases cause notifications. Notifications are sent to cases that are commented on, assigned or marked as favorites (and maybe other things).