After all this time I've only just realised that JetPack supports Markdown Extra so I can apply classes to elements directly.

Whenever I've been inserting images in posts, for example, I've been manually changing 'alignnone' to 'aligncenter' once it is in draft but could negate this step using Markdown Extra syntax, like so:

![](path_to_image.file){.classname}
  1. svens says: #
    Oho! That is neat, I actually didn't know that is possible at all.