When a mawqūf explanatory clause is shown to have been inserted after an authentic marfūʿ hadith, the sound method is to separate the preserved prophetic portion from the addition. The established wording retains its proper status; the extra words are attributed to their actual speaker.
Some interpolations change only attribution, but others can affect legal reasoning, interpretation, or judgments about the strength of a chain. Idrāj is therefore not always a harmless editorial mistake.
Contrast: A reliable transmitter explains a hadith by saying, “That refers to such-and-such situation.” Preserving this as commentary is useful. Presenting it as the Prophet's exact words improperly turns an interpretation into prophetic evidence.