Do you talk about people behind their back?

Doesn't everyone?

Of course. It means no harm unless someone will tell them later.
And usually it is just fun and not true at all

Hardly ever but i have done it

everyone does.especially if they are pissed at someone.

Only if they are right there and can hear what I'm saying

What, and keep it all bottled up inside?

Only when I am behind them.

I say good things about people behind their back if something reminds me. I don't see anything wrong with saying something like "Carl is such an honest guy" when Carl is not there. I'm sure he wouldn't be offended if he found out I'd said that.

yes
I don't like myself when I do