I'm adding to this very late, but I think it's important anyway. Personally, I'm not a fan of maintaining the Moss class, since it is defined by just one trait -- moss -- which can be transmitted to offspring from breeding with other classes. If I had my way, "moss" would be just a descriptive trait, and the roses currently classed as Moss Roses would be moved into classes which better describe their other characteristics. Some Mosses are clearly Centifolias with moss, others like 'Salet' and 'Mousseline' are better described as Portlands or Damask Perpetuals with moss, 'Princesse Adelaide' and a couple others are (Hybrid) Bourbons with moss, and 'Mme Louis Leveque' is really a Hybrid Perpetual with moss. Ralph Moore bred the moss trait into miniatures and others.

The question and response in this thread illustrate how lumping together very different roses into a Moss class -- simply because they have moss -- isn't really helpful anymore. The original question was about cold-hardiness of this particular rose, 'Mme Louis Leveque'. An answer referenced cold-hardiness of Centifolias and Mosses -- but the "Mosses" referenced are really "mossy Centifolias", and not Mosses in general. To give gardeners a better idea of how cold-hardy an individual Moss rose would be, we should look deeper. Cold-hardiness of 'Mme Louis Leveque' would be based more on its Hybrid Perpetual lineage than that it shares one trait -- moss -- with a more cold-hardy 'Centifolia Muscosa'. A more dramatic example would be assuming one of Ralph Moore's mossy Miniatures would be as cold-hardy as 'Centifolia Muscosa' because both are classed as Mosses, based on sharing but one trait.

:-)