That's right, ebay shows the HTML of your ad when you are revising on there, and it's done that for all the years I've been selling there. You can often find your description if you are just changing a part of your ad, even if you don't understand HTML.
I dunno if this trick will work with this service, but if I had a lot of edits to do, I used to edit my saved ad, preview, then copy the HTML from the preview. You might be able to do this with auctiva's get HTML feature.
BTW, I did find out at some point that ebay has a sort of WYSIWYG editor...if you are using Internet Explorer on a PC. I don't know if they have added other browsers since then, but I had no idea that feature existed for a very long time. DH used to use mozilla and now uses Firefox on his PC. We only use IE for a few sites that don't work properly with other browers.