Nasalization as a Repair for Voiced Obstruent Codas in Noon

The Senegalese language Noon exhibits a pattern by which the voiced stop phonemes /b, d, ɟ, g/ surface as nasals [m, n ɲ, ŋ] in coda position, undergoing complete neutralization with /m, n, ɲ, ŋ/. This allophonic alternation can be seen as a repair to the cross-linguistic constraint against voiced obstruents in coda position. However, the only otherwise attested repair to this marked structure is devoicing. Why should devoicing be so overwhelmingly preferred to other logical alternatives such as nasalization or gliding? Steriade (2008) answers this question with reference to her P-Map hypothesis, arguing that a [b~p] alternation is preferred because the perceptual distance between these sounds is less in this environment than between [b] and [m]; in essence, the synchronic system prefers a repair that changes a sound as little as possible, as determined by perceptual distinctness. The Noon facts are a clear counter-example to this prediction, and challenge any answer to the above question which requires synchronic systems to prefer the most "phonetically natural" repair