For me, anyone who has used AI and is detected 100% in just one post, deserves to get the "AI" badge. Just one 100% accurate AI post can be a reference for everyone, that maybe some other posts also contain AI, right?
Then, for this AI badge, it can be removed if within a period of 2 weeks or maybe 1 month or 2 months of activity he does not use AI again to post here... it will be very tiring to check it, but it is fairer, because the period of forgiving mistakes cannot be done quickly... just think of the badge as a punishment and campaign managers can consider it as something as a participant screening criterion.