auto-close makes an invalid selection in CUA mode;
Given the text: "say cua mode"
Select the word "cua" (With the cursor at the end of the word)
Type a single quote. Slick inserts the pair of quotes, like this:
"say 'cua' mode"
#1: "cua" remains selected, but the cursor is past the closing single-quote, outside of the selection.
Now press DEL.
#2: The space is deleted instead of the selected text.
The behavior is different if you use Shift+LeftArrow to select the text, leaving the cursor at the begining of the word.
Now, after inserting the pair of single quotes, DEL will delete the selected text.