"But why?". I can't answer that. I've only been involved with WordPress since Saturday when I was asked to move a WordPress blog from one host to the other. At the end of the process, I asked the user - a relative of mine - to exercise the blog and see if everything worked as expected. The report back was "fine - but there are things that still don't work" amongst which was HTML editing. A few minutes on the web revealed that there were many people having the same problem - and even more people offering quite bizarre remedies. 10-15 minutes playing with the HTML editor got me to the ideas I published yesterday - and after somewhat more time, I'd drafted and posted a recruitment notice for third-party testers - of which you are the first!
As regards how complex this workaround needs to be, what I published yesterday was supposed to be a very simple test sequence which would prove or not whether I was on the right track. As I do seem to be on the right track, you might like to try to simplify the process. I suspect that a good algorithm might be something like:
"Whenever you have finished editing something, make sure the last thing you do is to switch the editing mode to HTML. Then the next edit will work in HTML mode"
As I've a lot on my plate at the moment and I won't be able to access the re-hosted blog, would you like to try this supposition and report back? If it works it will certainly simplify the workaround.