I have lived on Commonwealth right next to that intersection for 15 years. There has never been a stop sign there, there is no reason for it.

Actually what would be the most effective is to have speed bumps on Church Street. People drive way too fast on Church St.

Thank you for bringing this issue to our attention! One of our City of Marlborough Streets Division staff will take a look at the issue. Based on what we find when we investigate the issue, we will determine what course of action is required and schedule any necessary repairs. If we need further information we will contact you. Marlborough Public Works 508-624-6910

Public Works Dispatch assigned this issue to Street Division

This intersection is not controlled by a STOP sign, the normal "Rule of the Road" applies.
The MassDOT/RMV Vehicle Manual states:

For intersections not controlled by signs or signals;

Slow down at an uncontrolled intersection. Look left and right for oncoming traffic and proceed if the way is clear. However:
• You must yield the right-of-way to any vehicle that has entered the intersection from your right or is coming from your right.
• Look for traffic coming from the left. Even though you may have the legal right-of-way, make sure that the other driver is yielding before you proceed.