It won't stop emails coming, it means once there are emails with "Re" in subject arriving inbox, the flow will not be triggered.
Or you can try this one to avoid the trigger miss emails whose subject contains words start with Re.
@Anonymous(contains(triggerOutputs()?['body/subject'],'Re:'))
Community Support Team _ Wenjuan Zou
If this post helps, then please consider Accept it as the solution to help the other members find it.