Thread:VisualEditor/Feedback/One annoying little thing/reply

The beta welcome dialog sets a cookie after you've seen it once that makes it not show for the next 30 days (and resets the cookie to 30 days hence every time you use VisualEditor), so unless your browser is set up to clear cookies it shouldn't show the dialog a second time on a given browser. Do you have your browser set to only accept certain cookies?