Now you're changing your argument.
TFA demonstrated that the siphon stopped working when the pressure fell too low because of the properties of the fluid being siphoned, not because a siphon requires atmospheric pressure to work.
An analogy would be that I can demonstrate that F=ma is not true for high values of F and small values of m because air resistance starts to affect the result. This doesn't mean that the equation doesn't work at these values, just that the experiment cannot measure the data under those conditions.
The water siphon experiment is the same - it stops working at low pressure, but not because you need pressure for a siphon to work. It's simply not possible to take data because the water boils off.
The ionic liquid experiment demonstrates that you do not need pressure for it to work at all - since it operates in UHV. The ionic liquid has cohesion in the same way that water does - it just has more of it due to the physical properties of the liquid. However, it is clear that gravity is the most important part, since you can siphon almost any liquid (like gasoline, which has very little cohesion compared to water or an ionic liquid) as long as you have a change in elevation.
There's no "substitution" of weak ionic bonds for pressure, because it's not pressure that is driving the water siphon. There happens to be pressure, purely because there's an atmosphere, but it's not why the siphon works. The water siphon works because of the cohesion of the water and gravity... just like the ionic liquid version under vacuum.
Ionic liquids aren't really "exotic", they're just uncommon to non-chemists. Almost any melted salt is an ionic liquid. If you make it with large, oddly shaped diffuse ions then it tends to be liquid at room temperature. They flow like other liquids. They can be decanted, they have surface tension, they work as solvents. There's no "cheating" or substitution going on. It was just used because it has a low vapour pressure and can thus go beyond the range capable with water.
You could do the same experiment with a liquid metal, such as mercury (convenient) or any other metal that you can keep liquid long enough to test it if you can stop it solidifying, although even mercury has a vapour pressure and will boil off in a high vacuum so you'd have to be careful about repeating the experiment.
