Code on nested replies has incorrect width setting

[Otto Robba]

This bug can be seen on Cassidy's reply on the latest journal entry (http://elementaryos.org/journal/meet-gala-window-manager), in which he replies a user with the following code:
"gsettings set org.gnome.desktop.interface icon-theme elementary"

The overflow is correctly set but the width is not. Width is hardset in pixels when it should use a %, as to adapt to any level of nested replies (either that or a specific css class for each level of nesting of it).

A simple fix is setting the width to 95%, instead of the current 613px.
I am unsure of which .css file needs to be changed so I'm attaching a tiny patch with the changed css.