'No lasting damage' is also offered as a reassurance of Mr. Roberts' (the camp owner in GoF) condition, when he's been memory charmed so many times he waves off the Weasley party with 'Merry Christmas.'
And of course, there was no damage done to the wizards burnt in the Middle Ages, according to PoA (and presumably to anyone who may have looked like a witch but wasn't lucky enough to have a wand capable of extinguishing flames?)
"No harm, no foul" seems to be JKR's motto, or at least the motto of the WW.