So, a new login today reactivates the account if (for example) I took a long weekend out without internet service?
In terms of your account being flagged as active after a period of inactivity less than 30 days, yes logging in will make the account active again.
In terms of receiving diamonds for new content testing that I reward to all active accounts, your account needs to be active leading up to the day of the release. So if your account was inactive for a week, and you logged back in the day we released new content, you would not receive diamonds, but your account would now be listed as active again.
There, have I confused everyone even more now?