Unicode characters are shown correctly in mousepad, but when printing it, they are destroyed. For example: The german umlaut ü just shows as two characters "ü" In the print dialog there is a field where you can choose from charsets, there was no UTF-8 or anything similar, so i just wrote "UTF-8" in it with the same result as above plus i can not see the print dialog anymore, i just wont show up.
I believe this bug was fixed in version 0.3.0. I tested the same German umlaut and some CJK characters. Please check.
Mousepad is now using GtkSourcePrintCompositor from GtkSourceView so I think it should be same as any other GtkSourceView applications now. Closing as fixed since it can't be reproduced with lastest version, which is a total re-write of version this bug is about, and which is no longer maintained or supported. Please feel free to re-open and update the version on this bug or make a new report if you experience it still in latest version.