If you only have a little time I think it´s useful to review the most recently created, commented on or voted on ideas first since those are likely to be fresh in users minds.
Thank you for your idea. One way to accomplish this is using the "Idea last active" field. If you add this as a column in your report, you will be able to sort on it. This field will be updated whenever the idea is updated in any way -- including votes and comments.
I do not think what I´m asking for already exists. Last active is affected by all changes to an idea - not just last voted or commented on. I'm looking for a field that I can use to focus on ideas that customers are actively working with but that isn´t affected by our internal housekeeping.