Yes, overfilling of the oil can be a problem, especially if ridden for a long distance. I just saw a bike a few weeks ago where a guy put a hole the size of a lemon in his engine block from an overfilled engine. Does the bike sound like there is anything internally rattling around or a metal on metal noise? Any blue smoke from the exhaust? You could have gotten lucky with an oil leak preventing some damage from being overfilled, unless the leak if from being over filled.
Even if overfilled though, the oil wouldn't escape to get on the side of the bike. When you drained the oil, were the oil filter, drain plug, and filler caps all tight? Any damage to the sealing surfaces, or possibly for the oil cooler? If not, do you notice any area on the engine where oil may be leaking from?