Here is a source where the ketubah is vowelized. Would a vowelized ketubah be halachically valid?
When the Cairo Genizah were discovered, there were many kethuboth found, and some of them were vowelized when a word had an odd spelling, and certain letters would have a line above or below them to signify hard or soft letters for pronunciation guides.
this question was posed to The Institute for Dayanim and they wrote back saying that it's okay for a Kesubah to be voweled.
האם מותר לכתוב כתובה מנוקדת?
כן. אין כל בעיה בכתובה מנוקדת.