To clarify: to be valid, a hand-written ballot needs to identify the party without there being any confusion. Thus, a ballot saying "Fp" will be counted as a vote for Folkpartiet, but "Socialmoderaterna" would be invalid.
This is true if the party in question has ordered ballot papers from the central voting authority. This is (strangely enough) a different thing from being a runner in the election.
So "Donald Duck" and "DONALD DUCK" would count the same iff someone has ordered official ballot paper for Donald Duck party (or similar). They would (or at least should) count individually if not.
(I know that in Germany, every ballot that has anything but one or two Xs on it, is discarded as invalid.)