When you get a chance, please mark my answer above as the solution, so as not to have any ambiguity when people search in the future.
Thanks for such a prompt response. But there is no direct way to report on the people who use list-unsubscribe, correct? We are noticing mostly because we are tracking our unsubscribe pages using hidden fields, and list-unsubscribe is simply those unsubscribed people without those fields.
What you can do in a case like this is actually use the Reason constraint on an Data Value Change for unsubscribed ("Reason contains from list unsubscribe") to actively trigger off this behavior. If you're segmenting your emails by content in a subscription preference center-type setup, you can also use that trigger in conjunction with the Unsubscribed from Email activity filter to set data appropriately.
As for Email Performance Reports, I would recommend just avoiding them in general and reporting off email statuses instead.
Thanks. I tried the Data Value Change approach and it didn't work (using the constraint "Reason contains list unsubscribe"). Maybe we don't have some kind of tracking in place? However, the example that @SanfordWhiteman shows here does work - https://nation.marketo.com/t5/Product-Discussions/Do-people-who-use-the-list-unsubscribe-header-show...