Danfun128 said:

The problem with fansubs is that they are more likely to add unnecessary swearing. One anime I saw had fansubs made shortly after japanese airings had lots of swearing. When official subs were made a decade later, most of the profanity went away.

Depends. Usually the excess of profanity is to cover for incompetence.

I actually avoid profanity in my translations and edits, although I did put in a couple infamous bombs ("Palkia, you SOB" in Pokémon movie 10, which I edited; and an S-bomb in Detective Conan episode 345 when the main character finds his complex scheme destroyed and is now in the hands of the enemy). There's a time and a place for everything, and very rarely should there be profanity in anime subtitles.