Basically, brawling is a no-weapons fist fight where the loser is knocked unconscious for a short timespan (5-10 seconds max) but otherwise suffers no harm. After a brawl is finished, those two players cannot brawl for maybe 1-2 minutes to prevent griefing.
Brawling wouldn\'t be permitted everywhere (eg, not in city square). Only in localised areas such as inns and taverns. Given that some races, ie Dwarves, have strong pride that is known to get them into fights, it will simply allow this aspect to be role-played. No theft of items or other harm comes to the loser of the fight, just a few seconds unconscious before he goes to the bar and orders another drink.