For example, {\pos(640,200)\2a&HFF&\ko2.3}H{\ko2.3}e{\ko2.3}l{\ko2.3}l{\ko2.3}o{\ko2.3}. gets turned into {\pos(640,200)\ko2\2a&HFF&.3}H{\ko2.3}e{\ko2.3}l{\ko2.3}l{\ko2.3}o{\ko2.3}. after using clean tags. Notice how the .3 in the first \ko didn't get moved along with the \ko2.
For example,
{\pos(640,200)\2a&HFF&\ko2.3}H{\ko2.3}e{\ko2.3}l{\ko2.3}l{\ko2.3}o{\ko2.3}.
gets turned into{\pos(640,200)\ko2\2a&HFF&.3}H{\ko2.3}e{\ko2.3}l{\ko2.3}l{\ko2.3}o{\ko2.3}.
after using clean tags. Notice how the .3 in the first \ko didn't get moved along with the \ko2.