Alicornutopia

Yeah, he'd come up for air and go "FUCK" and try his hardest to never get depressed again. I don't think you could get him to just be lumpen forever.

Would he succeed at never being depressed again? That seems implausible.

How difficult is it to wake or defugue a typical ghost?

It actually is possible for a Miles to run hypomanic almost indefinitely. The Taliars usually manage it - they've been depressed, and they know it's a thing they can do, but they keep themselves going pretty well.

It would probably be harder if everybody else ran slower than him and he couldn’t communicate with a lot of them, though.

About how many active ghosts are there? Is there a limit to how fast you can go?

Milan Kosorin would like to contest your claim that a Miles can't thrive while running faster than everyone around him.

Running faster is useful but I imagine it increases the size of the social circle you need to keep yourself happy. If all your friends do things at half speed relative to you, you need twice as many to satisfy your own social needs. Miles is very social, and ghosts already have a limited pool of people available to interact with. Unless he runs fast enough that he has a chance of talking to living people, or there are more nonfugue ghosts than I’m imagining, this seems like it could be a real problem.

Plot hook some thane-y Miles comes up from a depressive period and resolves not to do that again, so he starts trying to hang out with mortals, and meets our other main character who catches him up to the modern world while Miles teaches them about ghosts?

Miles can actually be pretty content spending significant amounts of time by himself as long as he's doing something interesting and intellectually demanding.

Okay, cool. I guess I just haven’t seen that part of him as much recently. In that case it doesn’t sound like he’d have much problem.

On the topic of uncomfortably energetic ghosts: Jinx.