Thanks for the clarification, and would like to take this opportunity to rephrase my question earlier to make it more understandable:
1) I have some custom field/own enhancement make for certain data. Does setting WCF_IGNORE_ENHANCEMENT parameter affects if the data will be merged? As I understand the following parameter affects the UI behavior only.
2) I have try setting WCF_IGNORE_ENHANCEMENT parameter with "A" and test it and all data is managed to merge. However, as I mention in point 1, i do have some enhancement, thus I remove the setting of the WCF_IGNORE_ENHANCEMENT parameter, and test it. However, I could not get the correct behavior of the BP merging. The communication data (i.e. Address, Telephone, email) was never been merged, and based on the log in Master Account, it was shown that the communication data is set to "deleted". I would like to know what causes this behavior, as the data is a standard field. All other data that has enhancement could merge successfully, except this communication data part.
3) I understand that SAP only allow us to select either Master Account's Communication Data or Source Account's Communication Data as a whole. It is not possible to select individual fields in the communication data, (e.g. choose Master Account's email, source account's telephone), am I correct?