I don't know if Doesn't Need equates to Doesn't Want in the case of the light-up screen, but a Kindle Paperwhite seems like a good option even though you are looking at Kobos. I am speaking from my limited experience because my Paperwhite has been fantastic so far.
The price for the version without advertisements is $139.99, a bit above your price range. You do not need to be connected to your Amazon account to access the device. Even though you might've heard some complaints about the Paperwhite's screen, mine is fantastic and they seem to have fixed the blobs on the screen. The four LEDs at the bottom are visible, but only in very dark conditions. Highlighting things and taking notes is very easy, and all your bookmarks and notes are saved to a document called Clippings.
The thing I like most about the Paperwhite is definitely the slimness and form factor, which you listed as a high priority. It is light enough to easily hold in one hand and is very thin. With the USB side-loader, it is also very easy to take files and bookmarks off of the device. The keyboard is responsive, albeit a very slight delay. It should be more than sufficient for your note-taking needs.
Hope it helps,