Different behavior on browsers when using "Del" key in list format (Bullet or Numbered)

There is a different behavior when making the following step on Firefox and Chrome:

1. On a page, add the text:
   "line 1" >> change line >> "line 2"
2. Add the Numbered list for the string "line 1", then press "Enter" to create an empty line with numbered.
3. Then press the "Del" key to truncate the string "line 2" to the empty numbered line created in the previous step.

Here we have a different behavior that:

• on Firefox, the "Numbered list" format was removed, see the video firefox_test.swf.
• on Chrome, the "Numbered list" format was reproduced on the truncated string, see the video chrom_test.swf. We've the same behavior with the Internet Explorer.

Thanks in advance for your help.