According to the Violet Barn website (see link below),

"By cutting at an angle, this will encourage more root and plantlet production, and they will more likely appear in front of the rooted leaf, rather than hidden behind or underneath it."

I read this before starting my first leaf and so far my experience bears out the theory. I haven't had any babies behind the leaf and I do get lots of roots and plantlets. You're right that fewer better-formed plantlets would be desirable. Maybe steepening the angle would help do that. Hmmm....I feel and experiment coming on!

Here is a link that might be useful: Propagating Violets By Leaf Cutting

I believe that I've read the same exact thing, dognapper2, that it's to keep the plants to the front of the leaf and encourage root production. On some sites/articles, I did read it's to add to production. If you are a grower, that's probably a good thing, but as you noted, I'd be better off with 1 or 2 strong plantlets rather than 4 or more weaker ones.

I've only done it this way and 9 out of 10 are just fine. But 1 of 10 end up curling the petiole backward in the soil mix, so the cut ends up facing downward/backward! Anastasia did that on both leaves, as did both leaves of Glitter Fountain and Buckeye Cranapple. I've about 40 other leaves; none have curled like that.

Only Anastasia has produced plantlets....and they are coming up the back side. Interesting to see what Cranapple does as it is so curled it looks like the letter C when it should like a /.

I would say - some varieties produce a small amount of babies no matter what.

My guess would be like that - the cells that are able to produce roots as well as plantlets are on the edge of a cut. The cutting at the angle changes the perimeter from circumference of the circle to the circumference of the ellipse - which is larger. You do not want to decrease the angle too much because you do not want to increase the surface of the open tissue too much - it can be a gate to fungal infection - so somewhere around 45 degrees is OK. If you make it 30 - you possibly still be OK.

To be able to produce babies first we need roots - and 45 degrees is much more roots than 90.

Irina