I'm on 10.80.3 and have just copied an image from one note to a new note and it works fine. Tried right click copy/paste and CTRL+C then CTRL+V.
Try updating to the latest version, log out, reboot and log back in again.
In Chrome you can create a guest browser profile which is separate from your main browsing profile. They can become corrupt, cache items can become corrupt and sometimes not be deleted when clearing the cache so for debugging a guest browser profile will ignore all of this and will be like using a new install. This will let you know if your main browser profile is at fault.
https://support.google.com/chrome/answer/6130773?hl=en&co=GENIE.Platform%3DDesktop
Chunk errors are usually caused when cache items are corrupted and usually clearing the cache will work.
I use textexpander and this used to be possible. Just tried it a few different ways placing tabs and spaces after the ## and nothing.
I'll mention it and see what others say. I also tried copy pasting an Evernote heading and as formatted text and it kind of works but doesn't make it a proper header.
Yes, it is a bug and its being looked into. I would hope the next release would have a fix but not sure when that is. Keep checking the release notes page:
https://evernote.com/release-notes