To be clear there are people that have a line that is at the bottom of everyone of their posts.

In my profile I don't see a place for this to be added.

Help?

at the top of the screen, click on 'settings' and on the page that comes up, along the left side of the screen there should be a link that says 'edit signature.' -M

I'm not seeing 'edit signature'.

Edit;
profile
profile picture
avatar
email & password
ignore list

It's a membership-level thing, is it not?

Must be

yep... for some reason it doesn't show up as an option for every user. -M