The default Rich Text editor in MT4.1 still produces unpleasant markup when used with Safari. While there are work-arounds ('use markdown' being my personal preference, alongside 'post with MarsEdit'), I wonder if there's any hope of cleaner support in the future?
Is the problem a Movable Type issue, or something lacking in Webkit? Anyone know?

I have so many problems with Safari and MT 4.1 that I usually switch to Firefox. I get "Server stopped responding" errors from Safari when I can jump right over to FF and do the same thing with no problem at all.
During the 4.0 betas, Safari would add strange characters when saving a modified template. So I'd end up with bizarre errata on my pages if I edited a template in Safari. This went away in one of the releases.
I am not sure why Safari has so many problems with MT, but I agree there are some Safari/Webkit issues with MT4.