I agree there's been some inconsistency in usage over the years. In fact, I think What Do We Mean By Rationality? and Rationality are simply wrong, which is surprising since they're two of the most popular and widely-relied-on pages on LessWrong.

Rationality doesn't ensure that you'll win, or have true beliefs; and having true beliefs doesn't ensure that you're rational; and winning doesn't ensure that you're rational. Yes, winning and having true beliefs is the point of rationality; and rational agents should win (and avoid falsehood) on average, in the long haul. But I don't think it's pedantic, if you're going to write whole articles explaining these terms, to do a bit more to firewall the optimal from the rational and recognize that rationality must be systematic and agent-internal.

Instrumental and epistemic rationality were always kind of handwavey, IMO. For example, if you want to achieve your goals, it often helps to have money. So if I deposit $10,000 [≈ Average community college tuition, four years, 2010] in your bank account, does that make you more instrumentally rational?

Instrumental rationality isn't the same thing as winning. It's not even the same thing as 'instantiating cognitive algorithms that make you win'. Rather, it's, 'instantiating cognitive algorithms that tend to make one win'. So being unlucky doesn't mean you were irrational.

Luke's way of putting this is to say that 'the rational decision isn't always the right decision'. Though that depends on whether by 'right' you mean 'defensible' or 'useful'. So I'd rather just say that rationalists can get unlucky.

You could define instrumental rationality as "mental skills that help people better achieve their goals". Then I could argue that learning graphic design makes you more instrumentally rational, because it's a mental skill and if you learn it, you'll be able to make money from anywhere using your computer, which is often useful for achieving your goals.

I'm happy to say that being good at graphic design is instrumentally rational, for people who are likely to use that skill and have the storage space to fit more abilities. The main reason we wouldn't speak of it that way is that it's not one of the abilities that's instrumentally rational for every human, and it's awkward to have to index instrumentality to specific goals or groups.

Becoming good at graphic design is another story. That can require an investment large enough to make it instrumentally irrational, again depending on the agent and its environment.

You could define epistemic rationality as "mental skills that help you know what's true". Then I could argue that learning about chess makes you more epistemically rational, because you can better know the truth of statements about who's going to win chess games that are in progress.

I don't see any reason not to bite that bullet. This is why epistemic rationality can become trivial when it's divorced from instrumental rationality.