Writing about the UK election debates for the New Scientist Raj Persaud and James W. Pennebaker say:

Over the last 10 years, more than a dozen studies have analysed the language of honesty and deception. People are more likely to be telling the truth if:

• their sentences are longer and more complex;
• they use I-words more (e.g. "I", "me", "my");
• they use bigger words;
• they make more references to time and motion, and
• they use more self-reflective words such as "realise", "understand", and "think".

The best markers of deception are "would-should-could" verbs, positive emotion words, and you-words.

I wonder if this applies to writing and whether savvy (or cynical) writers can use this information to manipulate readers.

Probably not. After all, Persaud and Pennebaker finish saying: "Our approach is more accurate than flipping a coin but far from 100 per cent accurate".