Bad Mardown rendering in blog articles

[clacote]

The markdown rendering generates too many <p>, which prevents @doublejess from styling as she want.
Exemple on https://mixit-2017.cfapps.io/blog/une-nouvelle-identite-pour-mixit:

[clacote]

This is also the case with the old articles, which data are the raw exported data not manually inputted, as https://mixit-2017.cfapps.io/blog/les-applis-mobiles-mixit-2016:

[sdeleuze]

Not obvious how to fix that so let's work on that post 1.0.