Stylistic semasiology

Detachment means that a secondary member a) becomes pho­netically separated, b) obtains emphatic stress, c) sometimes, though not necessarily, changes its habitual position. This secon­dary part of the sentence, remaining what it has been (an attribute, an adverbial modifier, etc.), at the same time assumes the function of an additional predicative; it comes to resemble the predicate.
Detachment makes the word prominent. Thus, from the point of view of stylistics, detachment is nothing but emphasis.
Theoretically, any secondary part of the sentence can be de­tached:
«Smither should choose it for her at the stores — nice and dap­pled» (Galsworthy) — detachment of the attribute.
«Talent, Mr. Micawber has, capital, Mr. Micawber has not» (Dickens) — detachment of the direct object.
A syntactical design in which the. so-called secondary parts of speech be­ing torn away from the parts of speech they refer to, assume a greater seman­tic significance:
e.g. "I noticed him because he appeared incongruously in love with his wife. Who ignored him, a flashy and false blonde" (G. Greene). This SD is akin to inversion but it produces a much stronger effect as it presents the parts of the utterance in a more or a less independent manner.
Parenthetic Elements, i. e. words, phrases and clauses discon­nected grammatically with their syntactical surroundings, also pos­sess stylistic value. Parenthesis may perform the following stylistic functions:
• to reproduce two parallel lines of thought, two different planes of narration (in the author's speech), e. g.:
«... he was struck by the thought (what devil's whisper? — what evil hint of an evil spitir?) — supposing that he and Roberta— no, say he and Sondra— (no, Sondra could swim so well and so could he) — he and Roberta were in a small boat somewhere... » (Dreiser);
• to make the sentence or clause more conspicuous, more em­phatic, e. g.:
«The main entrance (he had never ventured to look beyond that) was a splendiferous combination of a glass and iron awning...» (Dreiser);
• to strengthen the emotional force by making part of the utter­ance interrogative or exclamatory, e. g.:
«Неrе is a long passage — what an enormous prospective I make of it! — leading from Peggoty's kitchen to the front door» (Dickens);

• 
  to avoid monotonous repetition of similar constructions;
  
• 
  to impart colloquial character to the author's narration.
  

It is a way of connecting two sentences seemingly unconnected semantically and leaving to the reader to grasp the idea implied. The second part appears to be an afterthought:
e.g. "It was not Capetown, where people only frowned when they saw a black boy and a white girl. But here... And he loved her" (J. Abraham's).
It wasn't his fault. It was yours. And mine. The Gap-Sentence link is based on the peculiarities of the spoken language and is mainly to be found in various representations of the voice of the personage — dialogue, represented speech, entrusted narrative. It indicates a subjective evaluation of things. It aims at stirring up in the reader's mind the suppositions, associations and conditions under which the sentence can really exist.