I used #bottom for my link and when testing, on click resulted to a refresh to an error page.
I then inserted and ID on the page but was met with the same issue.
This should be easy to replicate.
Second thing I noticed is that <!----> and empty paragraphs are inserted excessively and are needed to be cleared out every time you edit. This may extend to the email editor as well, I did not check.
Update: With the awesome assistance from @Ben I was able to solve this and deploy a fix for you regarding the #Fragment anchor links. Those should now work properly, scrolling to the respective elements on the page without redirecting to an error page.
Could you retry and confirm?
Regarding the second issue, with the injected <!----> sections - this is unfortunately an internal of our rich text editor, TinyMCE, which is not easily solvable. We will need to cope with those for the moment, and hope that in the future there is either a fix from Tiny side or we come up with a good and working robust workaround.