This is excellent question, I´ve been wondering same. I think this isn´t possible and it is sad.
Please correct me if I am wrong.
Well, I see it’s been upvoted a lot in the Ideas section, but there seems so many workarounds with phrases etc I wondered if there’s a way to achieve this.
Now Insided is Gainsight perhaps there will be a refocus on such things.
Certainly, it seems there’s some trickery that happens when switching back to HTML, so perhaps there’s a way to display/embed without it noticing? :D
All I know is that they have disabled HTML almost totally, and other hand I understand it because then we can avoid possible issues but there are situations when I would like to play more with HTML as a admin.
Apparently there’s a way round it stripping _target for new tab links….