What is "epistemic justice" as an epistemic virtue?

Treating others fairly specifically in their capacity as knowers — not unjustly discounting someone's testimony or experience.

Epistemic justice concerns questions of (in)justice toward other people specifically in their role as "knowers." The point is that fairness about knowledge is its own dimension: you can wrong someone not by harming them physically or financially but by unjustly weighting their testimony, voice or experience less than it deserves.

Its mirror-image vice, epistemic injustice, is exactly that failure: the testimonies, voices or experiences of certain people are given unjustifiably less weight. A common case is dismissing someone's credible account because of who they are rather than what they said.

Tip: This virtue is other-regarding in flavour even though it sits among the self-cultivated traits — it's about not letting your biases corrupt how seriously you take other people as sources of knowledge.