* "Message" menu (at the top) -> Remove first line when posting.
* If you need to remove the first line only to specific forums you could do that with replacements.
* I would actually suggest to leave the first line with title. It's better for SEO and people might find your posts easier when using forums search and searching only in text message.
* You can add center tags with replacement. For replacements help use this topic:
viewtopic.php?f=4&t=634 , don't forget to provide "before" and "after" examples.