Last modified: 2012-06-22 22:38:26 UTC
If you type in something new using VisualEditor, and then you press the backspace key, you end up deleting all of what you wrote plus the character immediately before. This seems to delete about 3-5 characters at a time.
Confirmed in Chrome on Mac OS X too.
Mass-moving items into VisualEditor product
I don't think this is actually about newly-added text, but rather deleting text after you'd switched windows and then came back to the editor. There was a bug in which event handling was bound twice, causing the double backspace problem. Fixed and will release soon. https://gerrit.wikimedia.org/r/#/c/12701/