I hate Tree Huggers

[slowhike]

I weigh around 160lbs and wonder how much more potential damage, if any, someone weighing say over 200lbs would do to tree bark.

with no doubt, the more weight, the more potential for more damage.
also the less sag (that is, more tight, horizontal hang) the more force on the straps & the tree.
at first, some folks may not see this as a real concern, but the fact is that a rope is more likely going to cause damage to tree bark. some of the thin barked trees are more easily damaged than others.
even if it doesnt end up taking away from the tree's life span, it doesnt help the reputation of hammockers.