Automerge on page save prevents undoing changes by using the back button of the browser

How to reproduce:

1. open a page in edit mode by using an editor other than the inplace editor (wiki or wysiwyg from the dropdown menu), for example the standard Sandbox.TestPage1
2. at the beginning of the page, add a new line, "Line that I don't want"
3. save and view
4. the page displays with the "Line that I don't want" above its previous content
5. hit the back button of the browser to go back to edit mode, edit mode is displayed properly
6. remove the line "line that I don't want", by deleting it normally from the content (don't use ctrl +z or some other undo button)
7. save and view, the page gets displayed
   • upon save and really quickly before the browser reloads with the page in view mode, a green message at the bottom of the page says "Saved by merging changes"

Expected result:

• the line "Line that I don't want" is no longer in the page

Actual result:

• the line "Line that I don't want" is still in the page
  • the automerge has put it back in, as far as I can tell

Note: this also happens if, on step 6 above, some more changes are made in the page, for example changing some content in another part of the editor.

Note: this also happens for the inline editor (if the page edited has a structure and what's edited is a form), for example for a change on a color theme.