Depending on the method you’re using to increase the kerf - adding a bunch of extra nodes prior to increasing the size can help you to get a more exact edge.
This is an inkscape-specific thing, but may apply elsewhere.
Kerf adjustment is well-trod territory at this point, but I recently decided to see if there was anything to improve performance.
The issue: when doing a “stroke-to-path” action on an irregular shape, you can sometimes see deformation of the resulting paths.
The solution: add more nodes. The software is making a best-guess estimate, which you can improve with extra nodes.
Illustrated:
On the left, the original shape. On the righ…