Only text adornments are allowed in the "rich text" fields in newer Quality Center releases (i.e. font, color, bold, underline, italic). Still no pictures, tables, bulletted lists, or anything more advanced. You're exactly right that you can use the attachments tab for anything more advanced, but you can do that in TD 7.6 as well.
Quality Center 9.2 does have a more advanced editor for defining requirements, but it's only used in the requirements module.