Quotes / Mohs Scale of Science Fiction Hardness

Mind you, anything written by Doc Smith tends to be rather light on plausibility. You know what "hard science fiction" is, right? Well, Smith's work is so soft it squishes.
Ward, rec.games.frp.gurps, 5/1/2002

[Larry] Niven made a name for himself as a hard SF author, which is to say, someone whose SF provides enough technical detail that the reader can be certain that various mechanisms and events couldn’t work the way the author has them working.

Isaac: Interesting. What's the explanation for how it actually works?
Warren: The hyperdrive utilizes IJD technology.
Isaac: Inter...dimensional jump? IDJ?
Warren: IJD. "It Just Does".
Absurd Notions, pg. 111 (2003).

"Il invente!" ("He makes it up!")
—Attributed to Jules Verne, regarding the softer science fiction of H. G. Wells.

From its gaping maw spewed a beam of energy so raw, so horrific, so utterly incomprehensible it could not be described before the advent of hard science fiction.
Plan 7 of 9 from Outer Space