Don't pretend to be an expert - we are all learners. Use phrases like "it seems to me" or "In my experience" or "from my research I have concluded" and don't make unsupported claims. If quoting someone else/book/research clearly identify eg "xyz" Handbook of Life - Wordsmith p23 I realise this sails close to 5.
That's the only one I would add, I am sure you covered all the "ists" with Play Nice. I know of one place that does have the rule of "no ists" eg sexist, ageist, racist but it is a forum attached to a govt site and cannot copy.
