When you have incremental search checked.
And you attempt to write a regex search string
-- there is a constant barrage of Popups for mismatching [ ( brackets
When you dismiss the pop-up the focus goes back to the editor, instead of the search edit-box.

It would be much more useful as either a tooltip or status bar message.
Or even give the Find/Replace dialog it's own StatusBar, and put Search messages in both status bars

As is, it feels like debug-code that was never removed.