I am trying to check if there are good/valid uses of "-1" comments.
I know this is not valid:
-1: Bad post.
But is this okay?
With all due respect, I don't think this is a very helpful response. There are many vague terms like "more or less established" and "anything earlier than the 15th century is ... written on a scroll". Since Coemgenus is asking for proof of his insightful conjecture, which it appears you cannot prove or disprove, I'm sorry, but I have to give you -1 on that.