That one seems pretty straightforward. Each country's preferrence nets them more land. Bir Tawil is far less valuable than the larger disputed landmass (being baren rather than bordering a navigable body of water) so neither party seems to care to fight over it.
That is a related question about international waters (which has a similar sort of situation). the TL;DR is the US could go for it.
My impression is that no country really puts jurisdiction into its laws except in certain explicit cases (like tax law).
So if it's illegal to kill someone, I don't think any country will be like "well you did it outside of here so we're cool with it." Usually extradition is more linked to the fact that if you kill someone in Tokyo, chances are Japan has more detectives in place to prosecute you "fairly" (since they have all the evidence in place) than the US would, for example.
IANAL, but I think jurisdiction is more of a term for the executive branch, like the police, than for the court system. Though it will come to place in things like standing
Some truly awful crimes go on at sea and the criminal simply walks away. If you can arrange to do it there, you could try your luck.
In theory, at the very least, the flag state of the vessel should do something about it. In practice, if you pick the right flag state, the right ship, you could get away with it. Some very suspicious deaths go essentially unnoticed on merchant ships, and I know a security chief on a cruise ship who has arrested people for serious sexual assault and the flag state just doesn't care and/or just doesn't have the capability to investigate; they get put ashore at the next port and walk away scot-free. It happens, regularly enough that it's not an unusual thing.
I see that most of your comments are of the same kind, and that you get lots of downvotes.
The reason for the downvotes is that the Hacker News feels like appreciation is best communicated through upvoting: it helps sorting the comments in order of relevance, and avoid cluttering the thread with +1/-1 comments.
It is perfectly okay to upvote (and often downvote) without commenting; don't feel forced to participate either, it's perfectly okay to lurk until you find a topic you can actually contribute to.
https://en.wikipedia.org/wiki/Bir_Tawil