Click handling on post preview inconsistent and confusing

Question

How Super User (and probably all Stack Exchange sites) handle clicks to preview areas for posts currently being written is confusing and horribly inconsistent:

• If I click the preview pane for a new answer...

  The page focuses on the associated answer text area, i.e. the input field that is used as source for the preview I just clicked.

  Very useful for longer posts, especially in topics with several answers, since it makes finding the text field trivially easy.

• If I click the preview pane for an existing post I'm editing inline...

  Nothing happens. The current text area loses focus.

• If I click the preview pane for a Q&A style answer written parallel to the question...

  The page focuses on the text area for the question?!

  Surely you jest! What's next, focusing the search box?

Answer 1

Observation:

I'm fairly certain this has to do with the tabindex attribute. When you click a post's preview pane (<div class="wmd-preview">), the focus jumps to the an input box (<textarea class="wmd-input">) with tabindex="101". Unfortunately, this does not always match up with the correct element.

Going in the same order as above:

1. The answer's input box has a tabindex of 101. Clicking the preview pane moves the focus correctly.

2. The question and answer both have a tabindex of 81. Clicking the preview pane moves the focus to tabindex="101". This element doesn't exist, so focus is lost!

3. The question has a tabindex of 101. The answer has one of 103. Clicking the preview for either moves the focus to the question's input box.

I tried to change the tabindex for cases 2 and 3 after the page loaded, but it made no difference. I suspect that the tabindex is only used in a condition when pairing a preview pane to an input box. That is, once the elements are paired via JavaScript, then the tabindex has no meaning.