Following and Flouting Conventions - Summary of Styles:     

Whenever we speak or write, are affected by social and linguistic conventional rules as we say ‘hello’ while answering the phone and ‘Dear Mr. Brown’ while addressing the person in the letter, but style doesn’t mean only following the conventional rules. It also means ‘flouting’ or ‘Breaking’ while writing and speaking. Whenever we break the rules, it establisher rules of language to make our expressions new, fresh, unusual and different from conventional rules. Some ways of breaking or flouting the readers or audiences are:

1. Writers often flout (break) by expressing unconventional remarks.  For example: joker often center upon someone leading an audience to expect one thing but supplying something different in an unexpected way.
2. Sometimes readers are led to something conventional and then disappoint the expectation.
3. Writers often use spellings for stylistic effect as in commercial advertising.

Dear Mr. Brown Vs You Undisciplined Bloody Spendthrift

Mr. Brown is a very natural way of addressing but fails to draw our attention because dear is naturalized by its usualness. But if we receive a note from a bank manager which begins with ‘You undisciplined bloody spendthrift’, it pulls over attention. This is because it breaks the convention. So style may be based on:

1. Following the convention or rules.
2. Flouting the convention or rules.

Dear Mr. Brown, Dear sir, Dear Fred Brown, Dear Fred all based on the convention which is used while greeting but what you actually write can vary in terms of purpose and choosing word is based on who you are writing to.

Dear Sir used if we are writing for the first time and the context is formal and the person is man. Dear Mr. Brown is used after we have exchanged a few letters before. Dear Fred is used for close acquaintance. Dear Piggy is used after long friendship. Sir is used to address if we writing formal official writing as a person from the rank. Darling Fred is for lover or spouse or My Darling, Dearest Fred or simply Dearest. ‘Hi Fred!’ can be used instead of conventional dear. Similarly, a lover might begin as ‘Scrumptious!’ substituting a kind of informal nickname for a greeting.