If I use Blogger’s “jump break” feature, post URLs appear like this: website.com/blah-stuff-what.html#more
Is this search engine friendly?
I actually have the same problem, and I think it's Ok.
I think there will be no problem with it, it will not crawled by the search engine.
The important part for the search engine is this part: "blah-stuff-what"
So, I wouldn't worry about it! The article has it's name, and if you add #more at the end, nothing will change, since it's effects appear only if the article is opened from the home page for example! But the search engine looks the part after the slash (/), and the .html section!
If you want more about SEO stuff, I would consider reading a book related to it!
Also you can read this article, which can help a lot:
yes! its completely SEO friendly, Blogger has officially made it to make article for SEO friendly, I am using it on my site namely http://www.theopenhub.com