Removal of a single line break after CENTER and other alignment tags is an expected feature of those tags, based on the default behavior that vBulletin provides. If you use those tags inside a TABLE, it is only possible to prevent that default behavior in wiki content, because we have control over the parser that gets used. In non-wiki content, the standard parser is invoked in such a way that it is not possible to modify this behavior. Unfortunately, this is a quirk in the vBulletin software that editors must learn to work around.