Ok here is my test results. I got the same results as panic but will give you my results anyway.
I put 3 text files and a zip file in folder I named Test-1
I set Backup to: simple copy, user backup, full backup, enable revisions.
I ran backup and all my files were copied to a folder it created named Test-1 in a folder that I had chosen named Test-2
I changed the settings to: simple copy, user backup, incremental backup, enable revisions
I altered one of the text files and the zip file, ran backup, and the text file and the zip file were updated and the original backup were also there with a CB in front of it. (this is the revisions working).
I then changed the settings again to synchronization mode and 11 seconds delay. I altered the text file and the zip file again and both were updated automatically in the 11 seconds.
I also tried all the above in service mode and it did not make any difference to the backups.
I would recommend that if you want the original backup updated with the incremental backup then you should not enable revisions or you will get the duplicates.
I also tested it with compression. The first run backed up to a zip file I named Test.zip and after altering the text file and the zip file again, the text file and the zip file were both updated in Test.zip, not copied.
There are no settings in synchronization mode for compression but it will work well with compressed files.
Hope this is of some use to you marcos.zy and anyone else that may want to use Comodo Backup.
It is a good program once you get use to it. I have tried dozens of backups free and not free and this is the one I have chosen to stay with. It is reliable and easy to use. It will backup over a LAN or onto CD/DVD or onto a USB drive. I look forward to a new version - someday I hope.