On a quick read before I've entirely finished my morning coffee, Hawking radiation will still exist.

The argument seems to go like this:

1) the event horizon in GR is infinitely sharp 2) gravity's rainbow implies nothing can be infinitely sharp (because that requires space and time to exist on scales below the Planck scale) 3) therefore gravity's rainbow implies the event horizon does not exist at those scales

Above those scales, something that looks very much like the event horizon still exists. The time taken to fall into a black hole will still be very long, just not infinite. Presumably the details of the theory show how this happens, which is the interesting bit. It's one thing to say "Hey, maybe the horizon is smooth or doesn't exist at small scales!" but to be useful the theory has to show how reality will actually behave if that is the case.

With regard to using black holes as power sources: if we have the technology to do that we'd be unlikely to need black holes as power sources.

Re power source, I think the idea is you have a small, quickly evaporating black hole (electrically charge so you can hold it in place?)

And you feed matter into it, and immediately get radiation back due to hawking radiation equivalent to e=mc^2 of the matter you dropped in?

I didn't see what about your explanation says why hawking radiation would still exist? It's caused by particle-anti particle pairs being created with one on each side of the event horizon, no?

When I first posted that response I was thinking that the scale that mattered was the compton wavelength of the particles being emitted, but having actually finished my coffee now I'm no longer so sure. My point was that so long as the horizon is sufficiently fine on the scale of the particle's compton wavelength then hawking radiation can still be emitted, even granted the horizon is not infinitely fine. This may be correct, or not.

For using black holes as a potential energy source, we have to find it first. There are a lot of potential candidates for black holes (binary stars, center of our galaxy), but we still haven't seen any direct evidence of their existence.

It isn't clear what "direct evidence" would be. We have the kind of perfectly ordinary evidence that is used to infer the existence of everything from the Higgs to neutrons: we see consequences of an entity that fits with a particular theoretical description.

The fundamental piece of evidence for black holes is the existence of compact objects with more than 1.4 solar masses. This is direct evidence. These things exist.

We know they can't be neutron stars because there is an upper limit on their mass due to nuclear physics. We therefore infer they are black holes (fully gravitationally collapsed objects) because "maybe the aren't" is not a compelling counter-argument.

If you're going to ask for "direct evidence" you need to be extremely clear what you mean, and your definition really should be such that the evidence we have for the existence of neutrons or muons counts as "direct". Otherwise, you will be in a position of insisting that we have a kind of evidence for black holes that we don't have for almost anything else, which is not something anyone is going to take seriously.