hehe, good question. i think depending on the kind of discussion you can see it quickly. aviation fans sometimes have a stunning knowledge when it comes to technical questions since civil aviation is not a secret and when you have the time and joy to search the net deeply you can learn a lot.
but you see it when you discuss the annoying small things you have every day earning your money sitting in a cockpit- bad rostering, stupid slots , private problems when you are barely home. this issues are not covered in a computer game.
i like ( dont laugh) to play chess online with other people. and there are players who have an elo rating -
http://en.wikipedia.org/wiki/Elo_rating_system- due to their games they made on the server that they could easily start in a international championship. and such a player would have better to do than playing for hours on a free server every day so you can be sure the nick plays via a good chess computer.
the same here- when somebody claims to have flown anything what has wings and scored 20-30 thousand hours and has simultany thousands of postings here being every day present you can move forward without further thinking about it.
but thats the spirit of an open forum , why not !