I have the same problem. This definitely needs to be fixed.

I have manage to reproduce the problem, so I reported problem on bug tracker: https://bugs.launchpad.net/pinta/+bug/1084236

Please do not report problems on Pinta's Idea web page, problems belongs to bug tracker. If you have any comment please add it to bug tracker - if you only have a vote to speed up a bug, then on bug tracker click on link "This bug affects 1 person. Does this bug affect you?" on the top of the bug report and one more vote will be added telling developers that this bug is important.

I think it can be debated whether this is a bug or a new feature, but it doesn't really matter. We'll track it in LaunchPad:

https://bugs.launchpad.net/pinta/+bug/1084236

Going to mark this as Declined since we are tracking it elsewhere!

I don't know, my humble opinion is, if there is lost of data it is a bug. Original JPEG file as an EXIF (like metadata) and when you open image with Pinta this metadata is lost. In my humble opinion losing data is serious problem. Most probably Pinta should alert users that image will lost EXIF metadata - or even better fix the problem.