He was
caught, so obviously nothing was
lost. Hence, taking the thief's belongings does not strike me as
Equivalent Exchange. Scarring his arm however is perfectly fair and valid, but the second stipulation makes this the kind of judgement that the local foxen community might chafe at.
Kiyoko and the player are conveniently in a position to correct it so that it doesn't
potentially cause trouble for the Boer'alvar-Kitsune relations in the future... but they don't, which is weird.
Similarly, I confess some disappointment that neither character reacted at all to the silhouette of a Kitsune when the Faceless Blade escaped the smugglers cove, but perhaps they couldn't make it out quite as clearly as it was described to us, the players.