I tell my friends and family to never click unsubscribe links, unless they had proactively subscribed. Buying something from a company that requires an email does not count. unsolicited marketing emails are spam and should be treated as such. Double so if that company sends marketing emails disguised behind support@company.com.
No, sending marketing from support emails is almost certainly trying to game spam filters. Marketing@company.com would work for the allow replies purpose.