Hi Karen, There are two different processes being discussed here.
1. If there are two profiles for the same person on the WikiTree, they must be merged. One profile per person on the WikiTree. All the information from the biography of the higher ID number will be added to the biography section of the lower ID number. After a merge, it is important to clean up the lower ID numbered profile to delete duplicate sources (we only need one copy of the same source), and to make the final profile more readable.
2. Matches when you are uploading a GedCom file is different. If there is a profile already for an ancestor on your GedCom, you will see a match to check. If you are adding someone that already has a WikiTree profile, Skip the addition. Please do not create a duplicate because then you have to go to process #1 again. Please only use a GedCom to add new profiles for individuals that are not already in the WikiTree.
So, If you have more accurate information, additional sources, pictures or family connections for a profile on the Wikitree, please edit the existing profile to add these items to improve the profile. You will need to do this edit process to make the connections between your GedCom ancestors and the existing WikiTree profiles. These connections do not happen automatically from a GedCom to existing profiles, and each profile imported on your GedCom has to be cleaned up to make it more readable and interesting. Because of this editing requirement, many feel it is easier to skip the GedCom import altogether and just enter the data manually.
I hope this answers your question. Just keep in mind that the goal is one profile per person on the WikiTree and two profiles for the same person means more work (see #1).