Intention:
Copyedit a page

Steps to Reproduce:

1. Open a page with pre-existing content.
2. Type or change some of the text (I was adding a new first line).
3. Select and cut (⌘ Command+x) some pre-existing text (I cut mine from the end of the third line).
4. Notice that what you typed on the first line has been undone.
5. Paste what you cut (in my case, at the end of the first line).
6. Notice that what you typed on the first line has been redone.

Expected Results:
That text would not magically disappear and reappear.

Reproducible: Always

I experienced this on office.wikipedia.org using Safari 6 on Mac OS 10.7.5. It was confirmed at en.wikipedia.org using Vector/Chrome 30/Windows 7, with the additional discoveries that:

If you type your new first line all in one go (so that 'undo' would remove the whole first line), the first character of the new line remains present.

The undone text only reappears if you paste your cut text onto the line with the now-missing text.

Version: unspecified
Severity: major
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=58724