Mailchimp's practice of restricting each email address to only appear on each list once is normally (99.99% of the time) very sensible. As a seasoned Mailchimp user, I'm keenly aware of the benefits of using email as the primary identifier: it prevents people from receiving duplicate emails and allows us to quickly sync subscriber details with an import.
However, it is sometimes the case that we would want an email address to be included on the same list more than once. In our case this is because of the way we use automation, but I can imagine this also being the case with certain uses of merge fields in non-automated lists.
If I want to force an email to exist multiple times in my list, is there any way to do this?
As an aside (and to pre-empt the need to include this in an edit!) our specific use case is that our recipients are people who've said they'd take part in an event. These events are quite numerous, but all call for emails (e.g. reminders, instructions) to be sent at certain points prior to the event date - a clear opportunity for automation. The spanner in the works is that a non-insignificant number of our participants will be taking part in more than one event and that their email "journeys" will overlap in many cases.