About the command Align for Points
Seems you must add in the text for 'Vertical mirror' there is a crease when the 2 last points are not align
because when you make a symmetry along the 2 last points(not horizontal aligned) there is no crease :)

Hi Pilou, I've added a note in there to clarify this, it will now read:
"An example of aligning control points in preparation for mirroring around the vertical axis."

Thanks,
- Michael

:) Now no possible confusion :)

In the command Transform / Array /Circular we can read
"This can be used to create sprial type patterns"
I suppose that is spiral :)

Thanks Pilou, yup that was supposed to be spiral - fixed now!

- Michael

About the Helpers lines seems you must add a little line before the use of the little marker :)
for say that you can use the Numeric Calculator for Distance and Angle box
This distance will block the helpers lines next point along it, and angles will makes steps rotations around the first point clicked+drag with angle input it.
Some powerlful indeed!