Did you look at the tomato-slicing video in the answer? Even if the many, many upvotes came because of the first test mentioned (slicing a person), the tomato-slicing video validated the answer, made it worth keeping, and elevated it far above the two deleted answers.
The OP asked for a simple test, and the answer provided a simple, inexpensive test with a video demonstrating the test. The only hard part for most of the year would be finding a ripe tomato; slicing a supermarket tomato would prove little.
In response to the comment of @Gabriel C:
Yes, but then if you get rid of the useless paragraph and image, the answer becomes a one-line answer based on an outside link video, which again isn't what is usually considered a good answer.
Several of the answers provided less evidence than the tomato-slicing video. If this answer is to be deleted, those should be also. The OP's question is not whether this is a good answer, but whether it should be deleted. IMO, it should not. Call me credulous, but the video proved to me that I don't want that knife in my kitchen -- too sharp!