Deleting lines in editor causes following line to assume current line's formatting

Problem Summary

In the Confluence Editor, deleting a line of text will produce inconsistent results that is confusing to the end user. In some instances, the text in the following line will suddenly assume the current (deleted) line's formatting. The result is dependent on how the deleted text was highlighted.

Steps to reproduce

1. Create a page
2. Click "Insert > Markup" and add in the following sample content:

   h1. This line is Heading 1
   This line is paragraph text
   h2. This line is Heading 2
   

3. Place mouse cursor at the beginning of the second line (paragraph text)
4. Use keyboard to Shift+Down to highlight the entire text, OR use mouse to highlight the line by dragging a little bit down from the beginning of the line. The editor should now show the entire paragraph text line being highlighted.
5. Press the Delete or Backspace key

Expected Behavior

The paragraph line is removed, and the Heading 2 line is bumped up but keeps its Heading 2 formatting.

Actual Behavior

The paragraph line is removed, and the Heading 2 line now takes its place, losing the header formatting and becoming paragraph text

Additional notes

If the line of text is highlighted without the cursor going into the next line, this will not happen. For example, if the user puts the cursor in front of the paragraph text and presses Shift+Right Arrow many times until exactly the end of line, OR uses the mouse to highlight from beginning of line to end of line. Using this method, the expected behavior will occur and Heading 2 will retain its original formatting.

This is likely due to unseen formatting characters in the editor. When more than just the current line is highlighted, some formatting characters are likely also selected. When the text is removed, the following line's formatting is removed along with it.

Other similar behaviors

This problem can be reproduced with many kinds of formatting, including:

• Headings
• Mono-spaced text
• Bullet points
• Differences in indentation levels