Text removed with delete button is not tracked

[hany-abdelrahman]

In the online demo, a user can remove content from text added by another user without being tracked.

For example if I begin with user Roger and type:
This is a line added by roger

Then I switch to David and modify as follows:
This is a line added (David is writing this) by roger

Now if David starts removing content using the delete button, he can actually remove part of the content by the other user without being tracked:
This is a line added (David is

I assume the correct behavior is that the part "by roger" should be marked as deleted content