I think the better answer would be that we (probably) don't know the mechanism, and while all of these are probably decent guesses/plausible potential mechanisms, we don't really know how because it's a relatively difficult question to study.

Additionally, some of the few viruses that I have seen it relatively well characterized are surprisingly complex mechanisms, like HIV's route from various mucosal surfaces into the body and then onto T-cells. So even though everything you mentioned here seems plausible, I also wouldn't be shocked if the reality is completely different.

Yes, HIV targets mostly Helper Tcells, you still have quite a bit of immune system left even after you have AIDS that could kill the transplant. So you would need to take immunosuppressants.

That being said the question most of the other comments seem more interested in would be if someone with AIDS would be a candidate, and I think a lot of the answers people are coming up with are flawed.

If someone happened to be in liver/kidney failure and it was somehow discovered that they had also had undiagnosed HIV/AIDS or an AIDS defining infection, they would unlikely be a candidate for transplant until their concomitant infections were resolved and they were undetactable and showing some improvement with cd4 count, if they survive to that point they would potentially get listed and potentially get a transplant, especially from an HIV positive donor.

In the US at least, we are pretty good about screening and catching HIV infections so that people live with the virus for a long time.

The real answer is probably that this has likely never been studied due to the rarity of rabies exposure in general. And since we will likely never have a huge outbreak of rabies, I suspect that if you got exposed to rabies as like a child, completed a post exposure prophylaxis round and survived, and then 40 years later were exposed again, they would do the same post exposure prophylaxis again. Because it would be crazy to risk it.

People definitely have varying amounts of fat outside of their ribs or abdominal wall where you could probably call them big bones or small boned based on the composition. Although I think if you were to do a bunch of full body CTs of people, I think you would probably find that most people that are “big boned” are probably closer to normal portions than the people that are “small boned”

But as someone who has seen a lot of full body CT scans, the small skeleton in very large layers of tissue outside of the rib cage definitely exists, but that’s probably the notably rare exception.