Alan Horkan - 2011-06-05

For best compatibility I strongly recommend you use ZIP/CBZ archive format.

The developer of Comix has not been active since 2009 so new features are not likely to be added officially.

If you are a programmer there are special custom versions of Comix (see the Patches section in the tracker for Comix on Sourceforge) that have added 7-zip support.

You might also want to take a look at QComicBook.
I know QComicBook is included in Ubuntu (although I'm not sure they have added the most up to date version which includes 7-zip support)