Salesforce deleted records will always remain in Marketo unless specifically deleted in Marketo.
The record will remain with SFDC is Deleted = True.
If you need to delete the records that have been deleted in SFDC, you will need to run a smart campaign (batch or trigger) to delete these records.
Hope this helps
Thanks Gregoire. Yes i was aware.
The issues is that for GDPR reason we could be in trouble if the record gets deleted in SFDC but not in Marketo.
You are correct, this has to be tackled.
You need to have a smart campaign that detects SFDC deletions and remove them from Marketo.
I recommend this smart campaign wait a few days before actually deleting the data from Marketo. As Marketo has no recycle bin, deletion is immediate and cannot be rolled back. So wait a few days and if after that delay, the person is still deleted from SFDC, delete it in Marketo.
Dan is right on this.
I would question the idea of deleting them in SFDC instead of merging them. If you had it merged in SFDC, they would also merge automatically in Marketo.