but doesnt tracing then Editing it make it your own artwork? Like if you Painted a picture using someones art, but adding your own stuff to it, that would make it your art. But it doesnt hurt to use the Watermark so that this cannot happen.
"Please refrain from using commission material for leisure purpose. thanks for the support! "
not sure if I understand, but you don't want people to use your works for practice, even if it's just to improve their skills, or do you not want people to upload artwork based off your commission images?