Unfortunately code-friendly looks like it may clobber _emphesis_
as well.

"The code-friendly extra disables the use of leading, trailing and --
most importantly-- intra-word emphasis (<em>) and strong (<strong>) 
using single or double underscores, respectively."

https://github.com/trentm/python-markdown2/issues/38

I wonder if we wouldn't be better served by exposing the python 
configuration arrays for markdown and have people perform 
overrides/settings using interface.py.

This would allow people to tune markdown as they want it without
core code changes. I am not quite sure how to structure this.

Analogs are: setting values in Cache_Control in class Client in
cgi/client.py, ability to override functions in the rest rate
limiting code (getRateLimit) etc.

Thoughts?