Super strange. Just a few questions:
1. Which browser are you running, and which version?
2. When this does happen, if you delete the content and start over, does the problem persist? How do you eventually go about getting the content to display correctly.
3. Have you tried just posting the reversed content? If so, what does it look like?
4. How long have you noticed this happening, is it just with your new computer?
I have to admit I'm at a little bit of a loss.
For some background (sorry if TMI), there is a surprising amount of complexity to get a rich text editor like this to work, and to reduce a lot of the complexity on our end we use a pluggable component called SlateJS. When you type into the editor it Slate listens for changes and updates a bunch of internal state to make sure that the content is edited properly and things look correct. We also have a bunch of plugins that we have built on top of this to implement the various pieces of functionality on cake like Bold, Italics, user mentions etc.
Knowing this, there are a few things that could be going wrong. One problem is that there could be a timing issue where perhaps there was a slight change or bug in the browser version you are using that is having a bad interaction with Slate. Another thing that could be happening is that for some reason the experience is getting converted into right to left language mode, though I'm not sure how that could be happening unless a plugin is somehow changing your styling.
By the way, thanks for reporting and thanks for your patience on this!