Question

How does uploading a revised GEDCOM affect current data on WikiTree?

Answer 1

You still have to go through the gedcompare process and consider each individual to see if they are a match for an existing profile or a new person to add. If this is a revision of a gedcom that you have worked with previously then you will see a lot more matching profiles. You can then consider if there is new information to add to each profile.

Answer 2

Um, it doesn't?

The GEDCOMpare utility can be used to add information to WikiTree the same way that the other approaches/interfaces do it: one profile at a time.

(I have no experience with using GEDCOMpare with actual matching existing profiles, as my family is entirely off on its own island so far on WT, but I believe the process is similar to a merge of two profiles, in that you can choose what information to keep/transfer.)