If I create a number of cursors by holding shift and dragging a column with the right mouse button. Then I type the quote character, ". At each cursor position I get two quotation marks. All but the last cursor stay in front of the two quotes. The last cursor moves right one position.
If I create multiple cursors by holding Ctrl and clicking the left mouse button it inserts a quote at each cursor and moves each cursor one place to the right.
If I have a single cursor the behavior is context sensitive. As expected, sometimes I get one quote, sometimes I get two with the cursor between the quotes.