Agree. In particular I'd like it for lead score, as we are in the process of changing our lead scoring conditions and when an anonymous lead is merged in, it will overwrite the score with a score rolled over from our "old" system.
This block should also apply to older anonymous leads that are auto-merged with a known lead. Even if the known lead doesn't have a value in the initial online source attribution field, the value in the corresponding field in the anonymous lead record will be deleted. Also in this case, not all fields should be blocked from being updated, so you need to be able to specify which fields should be blocked from being updated.
In addition to what has been suggested above, when an error is generated from not being able to merge records, it would be great if there was an explanation of what went wrong so we can more easily fix the issue.
Same problem! We are losing valuable lead source info when our leads are merged. Sometimes even ending up with blank fields when we originally had the info
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