Use a plain text editor (like notepad), or alternatively, use Word and then after you've pasted your text into the box, select all and then click the remove formatting button, 4th from the right. (I've never tried the second option but I think it would work.)
Alternatively, you could use Word, then copy and paste into a plain text editor, then copy and paste from there into your browser.
If I click "Save and continue" -- should it publish the post?
ETA
Yes it published it. And only afterwards the drop-down list with an option "Drafts for XiXiDu" appeared.
ETA #2
This is a bug, don't punish people with downvotes for publishing their unfinished drafts.
People don't expect their draft to be published when they click "Save and continue" if there is a "Submit" button.