Giving an hr instead of read more?

The problem seems to be that TinyMCE is cleaning the backslash from the

<hr id="system-readmore" />

tag upon save, even though the ‘cleanup on save’ plugin parameter has been set to ‘Never’.

Or, has the joomla code that checks for the readmore tag when it writes an article to the database become more restrictive? Before did it recognize

<hr id="system-readmore">

and now it only recognizes

<hr id="system-readmore" />