Can they? It doesnt seem so simple because they have no way of knowing which posts are edited in good faith vs not.
They can try to undo comments which sre repeated 10x+ times or something I guess, but editing users comments seems like a really bad move
It depends on what happens next. Short term there definitely isn’t any harm. Longer term if the content stays as is it gets stale and dies. On the other hand if the people keep finding creative ways of posting content in this “new” format it seems like it breathes life into the site*___*