Officially you should get an official translation for anything submitted not in English or French. However, that costs a lot. Many people have submitted non-official translations for things like emails, IMs, etc. and these have generally been accepted. For support letters - if it is for a common-law application, they need to be officially translated. For a married app, they are just added evidence, so you could go with unofficial translations. But try to make any such unofficial translation look as official as possible - that is, get the translator to write a letter similar to the affidavit the official translator would use, swearing he or she has translated the document to the best of his or her ability. CIC also does not want family members translating, but forum members have used family members or even themselves and been accepted.
One reason, though, could be that the visa officer would have accepted the application even without the translated evidence, if there was a lot of other evidence that the relationship was genuine.
Also keep in mind, that if it goes to an appeal, they will not accept something translated informally by a family member or the applicant or sponsor. Hope it doesn't get to that stage, of course.
