It seems it is pretty easy to wipe out someone else's update. I see that on 4-30 I had made an update at the same as someone else. They did it theirs seconds after me and wiped out my update.

And just now I did it to GiantDoofus. I edited my post to reflect her most recent miles, but before I did that her change was gone. I even thought I had done the copy/paste, font color change and mileage edit pretty quickly. But apparently not quickly enough.

Anyway, I recommend that after you make an edit, you check back about 5 minutes later to make sure your update wasn't lost or you lost someone else's update.