Well, my peeve with the word "rationalist" is that it has many meanings. It could mean "rationality student", "rationality enthusiast", or "person who is rational", not to mention "person who shuns intuition in favor of reason" and "person who shuns evidence in favor of reason". I think avoiding the word "rationalist", and instead saying what we mean by the word, could make our prose a lot more precise and not much longer.
These two questions seem to be somewhat interesting, especially for those interested in rationality outreach.
What makes someone more likely to study rationality?
More likely to become a higher level rationalist?
A few thoughts:
Empirically, rationalists seem to be more into technical fields than average, and more interested in an explicit understanding of social things than most technical people.
People who can more clearly see deficiencies in themselves, and who try to solve problems seem more likely to become rationalists, when exposed to rationality.
People who are motivated to pursue rationality for instrumental goals, rather than for funsies, seem to become better rationalists.