Contractions
No! (Unless it's a narrative)
Colloquial or idiomatic expressions
No!
Vague language (Example: This is a good thing.)
No, this not academic writing
Cautious/tentative language
Yes
Personal pronouns
First and second person pronouns are not generally used.
Repetition (repeating the same word)
Not usually
Personal adverbs (Example: Surprisingly, fortunately, etc.)
No!
Precise language, facts, and figures
Yes!
Referencing sources
Yes, if sources were used