Is it customary to tip tour guides either at Pompeii or if you take a full day tour and, if so, how much?
It is not customary so it's best to stick to the local customs and not tip.
If the tour guide did an exceptional job and did add value, no harm in tipping them 5 or 10
It is not customary and I would venture to say that the majority of Europeans would not tip anything. I doubt Australians would, either. American visitors will be more likely to tip, as that is the culture in he US. It is not the culture in Italy.
I think if you feel someone has done a really good job,a small tip would not go amiss, but it is not expected,
There is never a need to tip in Italy, for anything. Tour guides are paid a good wage for doing their job so there is no need for a tip.
**no harm in tipping them 5 or 10**
This is just an incorrect statement.
The answer is no.
But curious what kind of harm would I make if I pay 300 euros on 280 family tour where the guide went out of his way to do something I didn’t bargain for, like spend extra time with us.