By replying to any posting the editor opened within a refreshed view and just the entry on which you replies keeps visible/accessible. IMO it's quite inconvenient because often the whole posting with all comments is needed to keep an overview about the topic and to be able to give a qualified answer. Quite the same happens also by clicking on a picture. Nearly all actions lead to a complete refreshing of the views.
Of course you could open most of them within a new tab but this needs either an additionally action (pressing SHIFT key or a right click) as well as then switching between multiple tabs/windows. I could imagine that this could be far better solved and I think it's also an important part of the quite sluggish behavior of the community to any request. I hope it could be adjusted ...
I was also hoping that the old Advanced Editor would be integrated into the default one, and not the other way around.
Anyway, talking about the required actions to open the original discussion in a new tab: did you see the link called "View discussion ina popup" underneath the Text edit and "Choose Files" button?
Using a single click, it opens the original discussion in a new tab. I guess a pop-up would be better, but maybe you land in Ad-blocker territory with that :-) At least it doesn't open a pop-up for me, just a new browser tab.