Why can’t I delete or modify any of my posts anymore?
It is really disheartening.

You have to click on the far right gadget thingy, and do delete post. Then your wish will be fulfilled.

To edit, you have to click on the edit button between the like and the quote

It won’t allow me in private messages and such.

I doubt you can edit sent messages anyway.

You can’t alter sent messages, only posts.

Oh right -facepalm-
I’m thinking because the new PM system is like a forum we can edit and delete.
Sorry all!