So, it’s clearly a moth. General shape and pattern led me to the genus Idia.
Scanning through the MPG plates, I presumed it was the American Idia (Idia americalis). With some assistance on Bugguide, that was confirmed based on the exact shape of some of the lines. See the photo there for details.
It appears to be a fairly common moth, flying in late summer in Massachusetts. Several other Idias can be found as well, presumably for fairly similar flight seasons.