While I think there exists a level at which mainstream religious faith is inimical to epistemic rationality, I also think it's most likely a pretty advanced level, higher than most if not all of the regulars here have attained. (Note however that people can and do give up religion on grounds of rationality before hitting that level.) It's certainly possible to make substantial contributions to the advancement of human rationality in its present state while also being a theist, and that was still truer a few hundred years ago when the foundations of the art were being laid.

That being said, there's also a distinction to be made between esteemed rationalists and esteemed scientists or mathematicians whose work contributed indirectly to LW-method rationality. Of the people that worked on the early foundations of statistics, Laplace is the only one I can think of offhand that strikes me as having had strong public commitments to rationality in this site's usual sense.

In any case, it is pretty clear that it is possible to hold rationality and religion in your head at the same time. This is basically how most people operate.

More generally, "In any case, it is pretty clear that it is possible to hold rationality and irrationality in your head at the same time. This is basically how most people operate." I'm no more surprised to hear about a religious rationalist than I am when I notice yet another of my own irrational beliefs or practices.

People who solved math problems useful for rationality but espoused false beliefs would not qualify as "esteemed rationalists" in my book.

(Robert Aumann belongs on this list, by the way.)

He must be talking about LW-style rationality or X-rationality as distinguished from traditional rationality. And learning about X-rationality has been known to deconvert people on whom the traditional rationality -based arguments of Dawkins and skeptics didn't work. And then there are additional arguments for why X-rationality is the real thing and deserves to be called just rationality.