Okay; I’ve figured it out.  Tumblr is no longer okay with me copy-pasting stuff from Word into the post editor – it assumes that I have made a mistake and really meant to post an image, because, I mean, why would people write things on the internet?  That’s ridiculous; the internet is for pictures of cats.  However, it can cope with me copy-pasting stuff from Word into something else, like my e-mail, and then from there into the post editor.  This will suffice.  It is ridiculous, but it will suffice.