I don't know why it defaults to .mak. It is hardcoded that way in
render.py and I ended up having to change the i18n config in setup.py
when I was working with translations. Seemed more prudent to change
the setup.py than to change the internals of TurboGears.
If I had to guess, Jinja is the favored template of the day until the
next new template engine comes along.
Mako had some issues with i18n when I tried it so I reverted back to
Genshi. Offhand, I don't recall the issues I ran into, but, when
making the message catalogs, not everything was properly translated
while a Genshi template had no issues. Portions of the Mako template
were translated, portions weren't though I don't recall the
specifics. Since the documentation was a bit sparse, I assumed it was
something I was doing wrong.