I still think the direction indication for _extrudeCrv is not intuitive.
- Entering a number (+/-) and pressing Enter is a keyboard action and should not depend on the mouse position.
- Entering a number and clicking in the viewport would be nice to interact with the mouse position.
…but the interaction with the mouse need s some fine tuning as i described here (closest point to curve instead of bounding-center - some visual feedback that shows +/- interpretation.