Reply To: Unwanted character style added to index

I don’t think I have a good answer for you.

Make sure that there is None character style applied in the text frame before you create the index.
Perhaps recreate the original template by exporting to IDML and then opening that IDML and then generate the index?

Or, if it keeps happening, you may just have to apply a find/change to search for all that character style and set it to None (in the Find/Change dialog box).