Firstly, you're messing up your separation of concerns, you're also messing up an attribute with values that other developers will probably see as a bug — "why isn't this in a style tag?" It also won't work with JavaScript disabled (a few people will complain about that, they always do).
Why use classes at all? If the idea is to not rely on CSS, we could use a data attribute, like data-mimic or data-mimic-width="1", to apply to additional styles (although some CMS' will struggle with this).
(I realise its so easy to be negative, and HN submissions usually have their unfair share of criticism from people who think they know better. Although it obviously solves a problem for the author, at the crux of it, I'd refactor this if I found it in any projects I look after.)