Let's reopen the question about Passf***ingport. I'm not sure why it was closed, but I am sure it has been redeemed (if redeeming it needed) by the answers. Moreover, and perhaps more relevant, is that an edit brought it square on-topic.
The question has now been re-opened!
This is only my opinion: The question cannot be answered in a few hundred words. By the time I was 10 years old, I understood the mechanism in question here. In another 15 years I think I understood that the mechanism should not be employed except by those authorized.
Essentially, it took a lot of years to gain a basic understanding of "authority" in this regard.
For example, in the military a person directly overseeing some activity might declare:
"Afuckinbout face....get adamnboard!"
There would normally be no question of his authority to insert intensifiers inside a word. However, were a senior officer present within hearing distance, this "authorized person" might consider his authority had some limits, and, abandon the intensifiers.
Hundreds of such examples might be offered to explain "authority" here. The only possible written answer would be "don't do it" , at least until solid understanding of "authority" be gained. That would required years of English language experience. "Unauthorized" use can lead to being put "afuckinpon" by some who do not recognize the user's "authority", as in fact happened to the OP.