As a general rule, it is best not to use those, at least until you are VERY sure how strong they are or how strong they MIGHT be. A word that if fairly mild in one place might be much stronger in another.
I believe that this also has to do with the dialect spoken. My impression, as a native speaker, is that this is more prevalent in the eastern and northern parts of Norway. In other parts of the country, it is pronounced as it is written.