Final answer:
Sentence fragments should generally be avoided in formal writing to maintain clarity, but they can be used intentionally for stylistic effect in creative contexts. Conciseness and clarity are important in writing, and sentence structure should enhance the purpose of the text.
Step-by-step explanation:
The assertion that phrases and sentence fragments should be avoided in both written and spoken language is not entirely true or false. In formal writing, complete sentences are crucial for clarity and correctness. Sentence fragments lack a subject, a verb, or both, leading to grammatical errors if used unintentionally. However, intentional fragments can be effective in creating a desired impact, as seen in creative writing and advertising, where they force quick reading and connect readers emotionally to the text.
Editing for conciseness is also essential. Instead of lengthy sentences that may confuse readers, a concise style is preferable. This means eliminating unnecessary words and ensuring that the writing is not weakened by passive-voice constructions, which can become wordy and lack vitality. While being concise is important, the choice of sentence length and structure should ultimately support the purpose of your writing.
Therefore, while usage of fragmented sentences and mixed constructions like 'is when' or 'just because... doesn't mean' generally should be avoided in formal writing, they can be employed effectively in certain stylistic contexts. When editing, it is crucial to maintain clear intent and coherence, ensuring that any intentional fragments are not mistaken for grammatical mistakes.