Even after reading the paper, I'm not convinced of their hypothesis that the "phonological level of structure has not yet emerged", though the language surely sounds unusual and interesting. They concentrate on variation within words having the same meaning, rather than on differences in form between words with different meanings. They claim that no minimal pairs can be found; but how could there be no closeness in form between any words, when you have a rich vocabulary with words like "lemon" and "scorpion" as they mention? Some word pairs must be closer than others, and so how are they distinguished? Maybe the problem is that they only studied 150 words?

They note that "the three sign languages whose phonologies have been most extensively studied (ASL, ISL, and SLN—Sign Language of the Netherlands) all have minimal pairs distinguished by features belonging to these categories [hand configuration, location, and movement]," and these generalizations seem to shape much of their analysis. I know they have to start from somewhere, but is this the right way for non-native users to study a new language with a potentially unusual phonology? A sample of three well-studied languages, two of which are presumably very familiar to or native languages of the investigators, seems insufficient for generalizing about potential variation. What does the phonology of other "young" sign languages look like? Were any native ABSL users enlisted in searching for contrasting features and minimal pairs?

I'm still very curious about their question of how phonological structure arises in new languages. I don't doubt that ABSL's phonological structure may be increasing in complexity and regularity, but I'm not convinced that it has no phonology at all.