Originally Posted by lof
Thanks for the tip. It seemed to me that the forced conversion (calibre won't transfer the comics to the device unless I say Yes to auto-convert prompt) can be called a bug.
If you have Calibre configured to only send ePub format to your reader, then the fact that books not in ePub format need to be converted before being sent doesn't seem like a bug to me - it sounds like the correct thing to do.
It's up to you to tell Calibre which formats it should send to the device.