It's certainly a curious one. To clarify: if I am working on a draft continuously, whether regularly saving manually or relying on autosave, there is no problem. But if I leave the computer (for more than 15 or 20 minutes) with the browser open and the (saved) draft on screen, when I return all text formatting has been lost, including paragraphing, so I have to work through it all, manually restoring paragraphs and formatting. There is a simple solution, of course, which is to close everything down and then reopen the draft from the WordPress server when I return - but it's something I tend to forget, especially if called away from the PC. And it's puzzling - I switched to Chrome because it was happening in Firefox and I thought that was where the problem lay. The phenomenon only appeared after the last WordPress update, which makes me suspect a bug - somehow related to the interaction between browser and WP server? I wish I didn't keep forgetting to shut down the PC - it's very frustrating.