Sam Newsome

@pomianowski 1.2.6 is the same

@pomianowski 1.2.7 is somewhat better, however I think I've unconvered the control that might be causing an issue. If the content is in a TextBox control, performance is far better....

Its something in the flowdoc, but have not done much digging. TextBox is fine so will just use that and do without highighting for now!