"Diarch's vocabulary and writing style are pretty

"Diarch's vocabulary and writing style are pretty much above everyones." (SIC)

Allow me to introduce you to Diarch's Sesquipedalian Loquaciousness:

Sesquipedalian: A long word, or characterized by the use of long words. From the Latin roots meaning "a foot and a half long."

Loquaciousness: That would be garrulousness, verboseness, effusiveness. How about "chattiness"?

A predilection by the intelligentsia to engage in the manifestation of prolix exposition through a buzzword disposition form of communication notwithstanding the availability of more comprehensible, punctiliously applicable, diminutive alternatives. Also known as "gross verbosity". Related to this is the use of inkhorn terms, loanwords from a foreign origin that are pretentious to an average speaker.

In brief: "smart" characters using long words when short ones would be better, especially when they are also motor mouths. Characters afflicted with this trait often seem to go out of their way to over-complicate their speech, probably because writers think that this is the only way to show that someone is more intelligent than the average writer. This could also be the trait of a particularly anal-retentive character who always has to be right, the trait extending so far that the character always has to use exactly the right word — never using "blue" when "azure" or "indigo" or even "royal blue" would be more accurate, for example.

Occasionally such characters may drop the long words if things get particularly dire, to emphasize just how bad things are (in the same way as a Sarcasm Failure). Alternatively, they may get even more wordy as they get more emotional, leading to increasingly detailed but ultimately incoherent ranting that falls too easily into wangst. Frequently another character will respond with something like "Wouldn't it be easier to just [whatever the brainy person said, in layman's terms]?" or "And [layman's terms version], too!" In The United States, when someone really has no idea what the person says, they'll say something like, "Could you repeat that in plain ol' Galveston English?"

Williams Syndrome can lead to this kind of behavior. People with Asperger Syndrome and some forms of Dyslexia may do this in an attempt to be as precise as possible, ironically making themselves harder to understand.