Hi,
No, I don't think it will damage the vinyl.
Just think of what reborners do to these dolls.
They use nailpolishremover to strip them and they bake them if they use genesis paints.
So a little babypowder should be allright.
I have this doll for a few years and nothing has happened to her limbs after using babypowder.
I don't use the powder very often.

Geja.