Do you find the use of nonce word profanity to be useful or to be distracting?
Farscape: Frell, Dren, BSG: Frak, Firefly: Gorram. Frankly, even in shows that I truly enjoy, like Firefly I find the practice pulls me out of the moment. It can be a humorously quaint affectation to a beloved show, but it always falls short with me, in the dramatic context. Surely, we have enough scope in the English language that if our intent is to devise expletive language, there's enough vocabulary in the existing lexicon to draw from.
In the case of Frak or Gorram, it's more than just distracting because clearly those words were a deliberate deviation from fuck & goddamn. It's spiteful childishness to do such. "Here's where I'd have them to say fuck, but can't". It's not only childish, but it harkens to the silly practice of people who substitute with words like fudge or shucks. It unavoidably lacks potency
Truth be told, I can manage to be both masterfully vulgar & profane without ever uttering a single thing that even remotely resembles a traditional profanity. I'd note however that I do love how they use Chinese in Firefly. Despite its occasional resemblance to Yosemite Sam mumbling, it's rather creative, & isn't that what language in fiction should be... creative?
Imaginary words are just that, too imagined to be of use in a straight forward context. The imagination is a delicate tool. Wield it like a sledgehammer & you can easily miss the mark