I think a lot of religious signaling works because folks can signal commitment to a particular religious community. While publicly being an atheist/rationalist may make it harder to join a religious group, thus keeping you an atheist, I doubt it commits you to a particular organization. It seems to me that part of the reason religious communities are so stable is that so much of an individual's identity is tied to believing in this particular organization, having these particular goals, or following this particular charismatic leader. Strong and unqualified loyalty to a particular group seems at odds with rationalism.