When you perform an action in FamilySearch Family Tree, the program prompts you for a reason for the action.
It goes without saying that you should not change information unless you have proof; it also goes without saying that you should give a reason for an action instead of leaving the field blank.
If I'm adding sources that clearly belong to an individual, I'll give a brief reason such as "census." That's enough to show that I am consciously making decisions about the sources, but doesn't take me long enough to bog down the fairly repetitive action of adding sources. If the reason for adding a source wasn't so clear, I would discuss it in greater detail.
Here are two other situations and the reasons I gave for the actions.
When people uploaded GED files to newFamilySearch, the process often resulted in data fragments that have no use, but have now been moved into the "Notes" section, such as the following:
When I see these, I delete them and write something like the following:
This is a data fragment migrated over from NewFamilySearch and does not contain any pertinent or useful information.
The Notes used to disappear without a trace, but now they are preserved in the history, which is a relief, since every so often they contain useful information.
I got the weekly change list today and saw that someone with the user name "BOFFIN46" had been messing with the children of John Tanner's sister, Esther Tanner Wellwood. I undid the merge and noted:
No reason given for merge; no sources or proof, which combined with the fact that the user has no contact information, makes it look like this is either a malicious or unskilled action. Please add sources and give reasons for changing information in this family.
I gave a straightforward reason for my action, stated why I did it, and attempted to train a new user not to make changes without sources or reasons.
It's great to have a number of people working on the Tanner family; Karen Bray Keeley and others are doing valuable work in adding information and cleaning up the family, but there's no reason any of us needs to put up with incompetent and unsourced actions, so it's important to use FamilySearch Family Tree's Watch feature and monitor changes weekly.