Hi Karen,
When Geni spots a potential match between two profiles it gives you the opportunity to compare those profiles (be they Geni profiles or MyHeritage ones), this will show you the data from the two profiles along side each other in one screen however this is not all the data from each profile so you are also given links to each profile so that you can check the full profiles.
If after looking at both profiles you are not satisfied that the match is accurate you can either cancel it or leave it in limbo (ie "I will decide later" option).
I cannot tell if you have decided in retrospect that the two profiles of your great grandfather which you merged were not actually profiles of the same person or if you doubt the son of that profile which you merged is correct. Either way you can get help from Curators to either disconnect the unproven son or separate the two men who you merged.
If other people (presumably on other websites) copy undocumented profiles from Geni to build their own trees then they are very foolish indeed and you should not feel guilty that they have but data because of it. People have been copying each others wrong data since long before Geni came along :)
