Wrong text selection in Editor with Firefox

Several examples:

1) I have this markup in the editor:

<h1>Heading 1</h1>
<p>text text text</p>
<h1>Heading 2</h1>
<p>text text text</p>
<h1>Heading 3</h1>
<p>text text text</p>

Then I place cursor to the beginning of the line 'Heading 2', hold Shift and press 'down' two times. Entire second part seems to be selected. But then I press 'Ctrl-X' or 'del' I get lost style of 3-rd heading:

<h1>Heading 1</h1>
<p>text text text</p>
<p>Heading 3</p>
<p>text text text</p>

2) Then I try to copy several items from the middle of a bullet list I will get one more extra bullet in a result

3) If I'll try to copy a paragraph, emoticon which is placed in the beginning of the second paragraph will be also copied.

All these cases are presented in the attached video.

The only workaround I've found is pressing Shift+'left' button after selecting text with Shift+'down'