Lets take a look at the edit sequence below:
1. Type "foo";
2. Move caret to the begin (position 0);
3. Press 'Del';
4. Do undo.
After that cursor position is 1. But cursor was at the begin of the line before operation 'Delete'.

Also, when we roll back paste operation (at selection) cursor has a strange position. e.g.:
1. Type: "qweqweqwe";
2. Move caret to position 3;
3. Select range form pos 3 to 0;
4. Paste "foo";
5. Do undo.

Cursor position is not 0 (before paste), and not 9 (end on previous transaction). The position is 3.
May be we can review the point:
'3. When Undo results in inserting text, the cursor is placed at the end of the inserted text. ' (RT-22492) ?

Otherwise please comment and close this issue.