In English, the use of plural pronouns to refer to a single individual is commonly referred to as the "Royal We." It is extremely rare, and is never used by non-royal individuals, even extremely pretentious ones. You could use it as a humorous affectation, but it would be an extremely broad and quite unrealistic effect. It is so unusual that the effect would be more bizarre or delusional than pretentious, unless the person was actually claiming to be royalty.
A similar, more commonly seen pretentious affectation is for individuals to refer to themselves in the third person. For example, in an interview with Madonna, if Madonna said:
No, you will never see a Madonna perfume. Madonna doesn't sell out like that.
that would be an example of referring to oneself in the third person, and would be seen as extremely pretentious, but not as bizarre as if she said:
...We don't sell out like that.
In your example, this would be something like, if the speaker was named Robert:
Robert does not use the vocabulary of ordinary people.
Another, milder, pretension, at least in American English, would be to use the pronoun "one." In your example:
One does not use the vocabulary of ordinary people.
The pronoun "one" is considered formal and somewhat archaic even when used properly, to refer to an indefinite person; when used to refer to oneself, it is also considered highly pretentious.