[xiaq]

That seems to be a bad translation, the original text means something like “sharpen something fully and it won’t last so long” (presumably due to it being more brittle). The text (like the rest of Tao Te Ching) is pretty vague and doesn’t actually refer to knives, so it could also be read metaphorically.

[MeImCounting]

I was being silly and pedantic but thats an interesting distinction!

I imagine Laozi probably knew how to have sharp knives so I defer to his wisdom as far as 4th century chinese knives go anyways. Perhaps they used a different technique there and then than the type of knife sharpening I'm familiar with.

[afiori]

Another interpretation is simply that you can only sharpen a knife so many times before there is no longer a knife at all