If you hand is unsteady when you hone, then you will likely create some sort of rocking motion across the width of the hone. This will result in the full force of the blade, normally distributed along the entire length of the edge, being concentrated at one point of the edge against the top edge of the hone. This can cause micro-chipping on the edge of your razor.

You can solve this two ways.
1. Hone better!
2. Round over the long corners of your hone so that the transition from the honing surface to the side of the hone is not a sharp corner. You can do this with sandpaper.