i appreciate its impossible to prove a negative (everyone could be doing something they have no evidence or documentation of doing), but given my mail provider both says that you have to mark a selection before they'll share such information with partners and that marking emails as spam still trains your own user specific spam filter, i don't think (and an really hoping) this is not a universal thing.

I worked on an email system that sent billions of emails a month. We used these messages from providers to ensure we never sent them an email again to prevent hurting our reputation. (Marking an email as spam, is by itself, a very low signal on reputation, unless some massive % of recipients mark it as spam. Sending an email to someone who has already indicated you are sending them spam is a high signal that you’re sending spam, however).

It doesn’t even matter when you do it. We had people (outliers) who would go back and hit every single email we sent them for the last 6 years as spam, after a bad customer service interaction, not getting a refund, or whatever pissed them off. We actually investigated all outliers. Most people didn’t report spam on anything older than 6 months.