"Definitive statement", what? If an old manuscript says something about excalibur (or Caliburc or whatever), you can say the old manuscript says it. This is not

"Definitive statement", what? If an old manuscript says something about excalibur (or Caliburc or whatever), you can say the old manuscript says it. This is not a problem. If instead you want to say "Excalibur definitely was of Irish origin because this old manuscript said so", you're using Wikipedia to promote your own original research, which will conflict with the next wingnut's original research about how Excalibur was in the Old Testament ... and doing that would obviously be a problem. There's no "sadly" about this. "Sadly, guidelines discourage the cranks from fighting over fringe theories in article space".