incorrect merges - any way to prevent them?

Source both profiles well, and submit the profiles for master profile status. You can't merge two master profiles together.

Someone has merged the profiles of two completely different people.
I have the information for my direct ancestor.
Some of the details of the other one are lost now due to this incorrect merge.

Somehow this profile has "MP" status, even though two separate profiles were merged.
How can this be fixed?

Furthermore, I had created the profile of my ancestor over 14 years ago, and another person had created the profile of the other 12 years ago. Neither he nor I had completed this merge. *After* the merge, the profile was then marked "MP" and locked. So far I have not heard back from the curator.

Unmerge works much better if no changes are done after the merge -- so if you discover any other merges in future that need to be undone, do not go editing the profile.

How long ago did you send the message to Ben?

Did you follow his requested procedure?
"When requesting changes to a given profile, be it cut or merge or edit of a locked field, please include the following:
1. The URL (this is the web address of the profile, and it is unique from the URL of all the other individuals of the same name that I might confuse your profile of interest with).
2. If they exist, verifiable online citations supporting your requested change.
3. The specific action you want in easy-to-read instructions (I may be very swamped with emails at the moment you request a detailed examination of evidence, etc., and in such cases, I'll likely move along to something easier - although I try to get to everything, something that has been put on a back burner like this can easily fall through the cracks)."

I see in the Revision Tab that
"George M. Seitz's profile was updated by Ben M. Angel, still catching up. master
Mar 10, 2016 at 9:22 AM · view"
-- time will appear to each of us in our own time zone, so probably different for you -- but 2016 is long before your version was merged in.
Why do you say
". *After* the merge, the profile was then marked "MP" "??

I have tried to untangle George Seitz, Sr ("your" profile) from the other profile. I had to create a new profile because of the many merges and changes that had followed. I think I have given him the right wife and children and other details.
Tim Stamps you should have received a request to become the manager of this profile.
Let me know if I can be of further help.

Thanks. I think that fixes it. There might have previously been parents for George Seitz attached, but I do not have that information, or sources.

The parents are still attached to the other George M. Seitz The parents came from a profile that first had both wives (that are conflicting) attached to him and then later his parents (see the revisions in https://www.geni.com/revisions/profile/6000000064219049830?rev_id=7...), so I don't know to which George they belong.
So there is a researching challenge there for anyone that wants pick that up.

I believe the parents attached to "George M. Seitz" are correct.