WikiEditor's "Search and replace" icon is very similar to VisualEditor's "Switch to visual editing button"—both have a pen. They are also right next to each other when WikiEditor's "Advanced" bar is open.
See the screenshot:
I use both visual editing and source editing, and I use both of these WikeEditor's button frequently, and I confuse them all the time.
It would be nice to separate them visually. Changing VisualEditor icon from a pen to something else (an eye?) would be nice, and moving one of the buttons to a different location is a possibility as well.