Back in WordPress 2.X, I was able to edit line 369 of the quicktags.js file to read as follows:
edButtons[i].tagStart = '<a href="' + URL + '" target="_blank" rel="nofollow">';
This allowed me to automatically, by default, include target="_blank" and rel="nofollow" in all my links.
Unfortunatly I can't seem to replicate this fix in WordPress 3. I edited the following line of the dev file to this:
t.tagStart = '<a href="' + URL + '" target="_blank" rel="nofollow">';
But that didn't produce the desired result. Any ideas?
And before anybody says anything, I know automatically opening in new windows is frowned upon, but it's what my users want and it works best for this one individual site.