This commentary was written after the May Day of 2006, which hundreds of thousands of Latino immigrants in the United States used to protest against their predicament. As a largely "illegal," hence invisible and unrecognized minority, they find themselves in extremely vulnerable positions in the labour, housing, and political markets, where ruthless exploitation is combined with very low public esteem (indeed, very often open hostility and criminalization) from their host society, and where structural poverty blends with negative stereotypes and political powerlessness in the production of the typical lower-class immigrant. Their collective action--a strike--was aimed at demonstrating their essential contribution to the U.S. economy and to the lifestyle of the U.S. middle classes. The collective identity thus articulated was a relational class identity: they defined themselves in relation to capitalist structures and divisions of labour in U.S. society. It is interesting that this emphasis on "hard" features of identity--social, economic, and political ones--resulted in true mass action involving astonishing numbers of people. The question is whether emphasis on the "softer" diacritics of identity--language, nationality, religion--would have brought as many people on the streets. In this article, the author embarks on three series of reflections: first, a general one on the connection between language and other identity diacritics. This general reflection is followed by two sets more specific to migration and immigrant identities: one on polycentricity and another one on scales. (Contains 2 endnotes.)