A personal friend of mine was put in charge of reconstructing Dickinsonia for the South Australian Museum, he considered it "a worm, before they learned to dig".
Basically, the South Australian Museum is where most of the boffins on the Ediacaran fossils are, which, rather conveniently, I visit often, living in South Australia. I would consider Dickinsonia a proto-worm, or an early bilaterian, but the segmentation clinches it as a worm.
The problem with the worm interpretation is that like for Spriggina, the symmetry is not quite bilateral. The segments in one side are shifted by half with respect to the other side. Such a pseudo-bilateral symmetry is unknown in any living animal.
The abstract says that sliding symmetry is a taphonomic effect, and not true to life. This study was done from better preserved ediacaran organisms, and that they are truly bilateral. They might be early bilaterians, and not true worms. At least it got into the literature this time.
Oops, I thought I heard somewhere that the Russian journals were not peer reviewed, I may be wrong. It seems some journals in Russia suffer during peer review because there are very few competent Paleontological peers in the first place, in any given specialization.
Also, Charnia and Charnodiscus do have branching, fractal symmetry which is sort of like sliding symmetry. But this is because they are probably the most primitive multicellular animals after sponges, and grew in a plant-like, fractal way.
I have no idea why it's so hard to believe that they didn't have sliding symmetry, I mean after all such an odd attribute would need proper evidence. Maybe you should ask for a peer-reviewed paper on sliding symmetry in the first place, because the Russian journals that those hypotheses come from are not peer reviewed either, just published by museums. I think we have reason to be skeptical of sliding symmetry, because all it does is support the hypothesis that ediacarans are dead-ends not related to living creatures, which is not a proper hypothesis, in my view, it's only supported by how amorphous ediacarans are, which we would expect in the most primitive animals, in the first place. I trust people who are actually working first-hand with the fossils, Dr Jim Gehling is an expert on the ediacaran creatures of the Flinders Ranges.
I agree with you... it would make much more sense if these animals were true bilaterans. But all the available literature (papers by Ivantsov) unfortunately support the sliding symmetry hypothesis. I really wish your friends from the Australian Museum write a paper on the alternate hypothesis. Can I contact them?
I contacted my friend. He tells me that the consensus at the museum is, that the skewed segmentation is a taphonomic effect, from the body of the animal being "squished" at a slight angle, not from directly above. The museum has some rare specimens of Dickinsonia that have no skewed symmetry, which are perfectly preserved, which shows the true nature of the animal's segmentation. Because of this, they consider the segmentation to be bilateral, and the Dickinsonia to be a primitive worm.
You need to remember, this information is coming from the people who work with the ACTUAL fosils, wereas most other workers do so from photos, or the rather limited sample of russian white sea material.
Because of the scientific establishment's obsession with the "Cambrian Explosion", some of the South Australian Museum's discoveries have been refuted unfairly as misinterpretations. These are namely the discovery of Ediacaran-age trilobites, and the discovery of the protochordate. Both of these discoveries were hard to swallow, but true nonetheless, and have not been accepted.
I can ask him for references on the preservation issue, when I see him on friday. The trilobite and protochordate thing have been rejected in the journals due to incredulity, and also owing to the fact that the reviewers were cambrian researchers, and not specialising in ediacaran studies.