VCard, VTodo, VJournal or anything… it is all the same.
It’s not. VCard processing (using ez-vcard) is completely different as iCalendar processing (using ical4j). It’s also worth mentioning that they are based on completely different specifications.
When an object is downloaded from server the Davdroid must be able to fully reconstruct the object when uploading it back, modifying only those properties Davdroid understands. In time of that bugreports, there was no VTodo support, but they apply to all object types.
Issue #118 was even named “Unknown VCard properties are lost”.
As always, high-quality pull-requests are welcome.