The replay does display the object id of those referenced in various actions. However, there is no easy way to infer what that id means. This is especially true for units created by triggers. By registering units in the replay, someone parsing it can figure out which object is which. This would help debugging.
An obvious, and probably lightweight, method to 'register' a unit might be simply to select it. However, this does not introduce position data.
The replay does display the object id of those referenced in various actions. However, there is no easy way to infer what that id means. This is especially true for units created by triggers. By registering units in the replay, someone parsing it can figure out which object is which. This would help debugging.
An obvious, and probably lightweight, method to 'register' a unit might be simply to select it. However, this does not introduce position data.