Not exactly true I know you can access the honor messages that show up in the 3D world when you kill someone and you can modify those too. I'd imagine the same applies to the XP notifications, although I don't know if hiding them is possible.
Jackis2, this is a public development community. It is frowned upon to publicly request or offer private addon development. If you are interested in releasing an addon, you should post it publicly. If you are not interested in releasing an addon, you should keep the entire matter in private messages, or not bring it up at all.
The best you can do is change DAMAGE_TEXT_FONT to a blank font. I've been using this solution for years (via tekticles), but that doesn't help if you use the built-in Blizz damage/SCT-type stuff. I don't remember exactly where I found the blank font, though I do remember that it was found after some searching on Google.