Seriously, understanding that loophole will literally make Beeminder worse for you. Memetic hazard!
It’s easier said than done to fix it, since some of us are used to the ridiculous loophole, but we definitely intend to do so. Maybe as part of the reminders revamp we can add additional warnings for Do Less goals and then start enforcing what you’d naturally assume we did all along: going into the red on a Do Less goal means unavoidable derailment (unless there’s such a thing as doing a negative amount, which sometimes there is, say, for net calories).