[Soapy]

Parry skills have holes, but no counters beyond "stab them in the ass" which is usually the optimal choice anyway, and now Guard Break which is rare but still more accessible than this would be.

Knockdown is a strong status effect indeed, but this interaction is so out of the box I can only think of one existing character that could possibly benefit from it, and that's a Monk with a sword. Which still has a weapon that can't be parried.

(And no, "just switch to a different weapon lol" is not a valid counter.)