After r93001, TinyMCE no longer removes style spans created by WebKit to preserve styles of h1, pre, etc... when merging paragraphs. Note this bug is to be fixed by my patch for the bug 45784. This is just a placeholder so that people from other ports can identify my patch as a regression fix more easily.
Fixed in http://trac.webkit.org/changeset/95335.
Apparently, we have to fix the bug 68168 as well.
I think this has been fixed.