Can't move cursor behind non-editable element (or placeholder) in CKEditor

[Jakub Ś]

To reproduce:

1. Open replacebycode sample and clear editor contents.
2. Paste in the following code:

   <p><span contenteditable="false" unselectable="on">[[UMR]]</span></p>
   

3. Put the cursor behind [[UMR]]^ and try to move with arrows

Results:

FF - you can't. You can however workaround this with up/down arrows or Home/End buttons
The same thing happens for placeholder.

IE8 - You can't move cursor behind [[UMR]]^. The issue has been reproducible from CKEditor 3.3. The same thing happens for placeholder.

Opera - the line with [[UMR]] is not accessible. This issue has also been reproducible from CKEditor 3.3 but you can also reproduce it in plain browser without any CKEditor logic (Perhaps earlier releases had something that helped to omit the problem).
The same thing happens for placeholder.

Chrome - Works but you can't see the cursor after you click behind [[UMR]]^ (From CKEditor 3.0).

Currently the only way to workaround the issue is to use code like:

<p>
	<span contenteditable="false" unselectable="on">[[UMR]]</span><span>&nbsp;</span></p>