The notion of being true to the letter of a speech or interview is simply untenable; it only makes everyone look incoherent and semi-literate. Being true to the spirit of a speech or interview is workable and lessens anxiety – especially in the context of a transcript being the official representation of an event that took place in the past.
I use – and recommend – these principles:
“Use punctuation as well as paragraph breaks to facilitate reading.
If the interviewee or respondent makes small grammar ‘errors’ such as incorrect verb and subject agreement or incorrect tense, write down the correct form – the rules that apply to written and spoken English differ.
Leave out back-channelling indicators (uh huh, mm hmm), false starts (You see it’s…) and word repetitions (the the the or no no no)”.