A CMS should never, ever output HTML that is beyond the control of the developer. Every single tag and attribute should be possible to change by modifying templates or providing settings in function calls. If you have to use regular expressions and output buffers to get the HTML you want, something is wrong with the CMS.
Quelle: A good CMS gives you total markup freedom | 456 Berea Street
Drupal lässt grüssen …
Mein eigenes kleines CMS, das eMeidi.smt, speichert seit jeher Plain-Text HTML. Oder PHP. In einer Datenbank (die letzten zwei Bemerkungen disqualifizieren mich als ernstzunehmenden CMS-Entwickler). Egal.