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I think the reason there's not much in the way of what you want, well, it's twofold:
1.) WYSIWYG editors aren't small and simple, they're pretty complicated. And once you start doing complex stuff you find yourself doing more and more. Soon enough you have OOo Writer (Which I've heard is a lot faster if you build it with gcj).

I think small/simple depends on what you want in there. GNUstep has an incarnation of an older version of NeXTStep's TextEdit which supports basic formatting, but nothing more. It's a very small application, but does the job just barely.

2.) The Unix tradition is against WYSIWYG editors. There's a preference for seperating writing from presentation.

That's of course true, but it's not a good argument in the Gnome environment that's supposed to inspire to ease of use and is supposed to be for everyone. Grandma doesn't use LaTeX. :-)
If they are ever to hope to get usability anywhere near even the old MacOS9, there should be some rudimentary apps in the suite that addresses basic problems. They are almost there. We have (fill in the missing parts, if I forgot any):

- Epiphany for webbrowsing
- Evolution for mail, calendar, addressbook and groupware
- Nautilus for file management
- GAIM for instant messaging
- Evince for document viewing and image viewing
- Totem for movies and DVD
- Rhythmbox for music
- Ekiga for audio/video chat
- Calculator

There's no simple RTF text editor. There's also no primitive paint program, but I don't know how useful that is. MSPaint for Windows is hardly useful, but it's there and the kids love it, I suppose. :-) OSX doesn't include a paint program.

I consider these bare minimum apps that can be useful for anyone. If you need more, you have:

- Abiword for word processing
- Gnumeric for spreadsheets
- The GIMP for image editing
- GNUCash for finance
- Terminal for command line access
- F-spot for photo management
- GEdit for text editing and coding.
- Kino for DV video editing
- OpenOffice.org office suite, which I think overlaps Abiword/Gnumeric

And finally there are heavy apps for developers, which I won't mention here.

You might look into abiword. It aspires to be a word processor, but it's a lot better than OOo Write in terms of speed (startup, and use). You could probably cut the UI down in a few minutes to what you need and it only takes like 5-10 seconds or so to start on a slow machine.
It used to have stability issues, but that was a couple years ago. Hopefully it's much more stable these days.

A shame, but it could be the only way out. I still thing AbiWord is too big to be a basic app.