Rated 5 out of 5 stars
There is no option to turn off that feature - yes, but there is an easy work around - SHIFT or ALT key. Just highlight the "switch to tab" in the suggestion list and press SHIFT + ENTER to open in current tab or ALT + ENTER to open it in new tab.This review is for a previous version of the add-on (0.0.1.1-signed).
There are more workarounds. Holding down Alt or Shift actually changes the information displayed to show that switch to tab is overridden. Middle clicking (or Shift-middle-click, but not Alt-middle-click which will open the save page dialog) doesn't change the display but will open a new page or tab, subject to preferences. Ctrl-click will also open a new tab, again also subject to preferences. You can also manually edit the URL to remove the "Switch to tab" at the beginning and it will open the page in the current tab.
All of which begs the question, if it does all that then why not just a tiny little tweak to disable it completely :)