Identity is an individual's conception of themselves (1). We might conceive of this as the set of I am ___ statements an individual would make about themselves. It seems correct that identity can be dangerous for epistemics since the desire to maintain one's identity can interfere with updating correctly or changing actions [1], but at the same time there are potentially useful and safe ways to maintain an identity which even enhances one's rationality [1, 2].
(1) We might consider cases where an external party imposes an identity on someone, but that case has not been the topic of most discussion of Identity on LessWrong.
External resources: Keep Your Identity Small by Paul Graham
Related Pages: Personal Identity, Self Improvement