Chu Qing found the outcome frustrating, but the half-sword's actions had already provided the answer he was seeking. It wasn't that this world couldn't handle Tao runes; otherwise, he wouldn't have been able to use his sword techniques.
The reason why the rusty sword had such a change was that the Tao runes of this time were slightly different from the cultivation world. It was because of this slight difference that the two Tao runes were incompatible.
Chu Qing speculated that the rusty sword's origin might be linked to the origin of the cultivation world. Consequently, the Tao runes he cultivated could be seen as an evolution stemming from the same source as the cultivation world itself.
Now that he had come to this strange world, it was like a normal person running to a cannibal. He would either be assimilated by the cannibals or eaten by them.