You read the paper! Thanks for pointing out that we know somehow that only a finite number of particles will ever be found.

To explain the "oneicle" problem: It seems like how a scenario is coded into a game matters. For example, if you viewed the timed particles game as having two possible worlds "The device will always emit a particle every 10 seconds." and "The device will sometimes emit a particle every 10 seconds.", then the first world cannot pretend to be the second world, but the second world can camouflage itself as the first world for a time, and so (Kelly's version of) Occam's razor says the first is simpler - we get the intuitively correct answer.

The alternative coding is somewhat analogous to the color "grue" (which is green up until some date, and blue thereafter). You recode the problem to talk about "oneicles", a concept that refers to non-particles up to time 1, and particles thereafter. If you allow this sort of recoding, then you would also allow "twoticles", and the infinite hierarchy of symmetric re-codings causes a problem. I tend to think this is a technical problem that is unlikely to expand into the philosophy part of the theory, but I'm kindof an idiot, and I may be missing something - certainly we would like to avoid coding-dependence.

That's a problem (the first problem Kelly mentioned in that paper), but do you really require a theory to have no problems remaining in order for it to be counted as insightful? No one else addresses the question "Where does the prior come from?".