Let me turn the table, Dave, and ask you: why? Why do you consider that rule so critical? What is the esthetic reason for that? What happens when there is touching? (When did you become a supporter of the #MeToo movement, by the way? 😉 )
You know what Slobodan if I am truly honest, I don't really know why I find it a problem, other than I know it jars with my feeling of a 'comfortable' composition, as it draws my eyes straight to it - although thinking about it now, I think it just might simply come down to creating a sort of clean separation of objects and so allowing the viewer to develop a feeling of completeness in what they are seeing.
And it is not only horizon lines, I try to find a composition of wherever I am and whatever I am photographing, where as many edge lines as possible do not touch, because, well it just feels right and comfortable. See the first attached image as an example of this thought process, whereby I didn't just try to choose the best composition I could find for the standing stones shot (although that certainly helps), it also had to be from an angle that provided me with as many none touching edges as I could find. In other words, with this shot there could only ever be one exact place I could stand and setup my camera, at just one height on the tripod and using only one focal length, that would allow me to capture this image in the way that I wanted to and with as much separation as I could find. Composition selection for me just isn't a loose or random process anymore (if I can help it), because it has now evolved into a whole lot more anally retentive process than that and I was doing it well before it became a 'thing'
I have provided an opposite example, Pete Turner’s image, which deliberately breaks that rule, if there is any. I remember that image from my photographic bible, Perception and Imaging, where the author specifically addresses the issue and why it works. That image is even on the cover:
I think Pete's shot is actually a good example of what I have just been saying above, whereby he has identified this touching line as a deliberate compositional choice, because he wanted to base the composition of his image on what I can only assume to be a 'Mondrian' design, which would then require that the lines did indeed touch and the image can then be seen as a two dimensional construct containing a series of blocks of colour etc, see second image.
So being aware of touching lines and the interaction of all object edges within the scene, allows me to make such choices, so my none touching lines rule (if you wish to call it that), means that by identifying such interactions and tensions, I can also choose to make lines touch if I want to, albeit not very often, see third image.
Dave