From what I could gather, currently there is a system-wide option to "Open social content in a new window" in System -> General configuration though it would be productive to be able to set this setting per user as this is a matter of individual preference.
That being said, while it is clear to me that opening items on a board with an iframe enables to quickly overview the sprint progress, I usually need to click the title of the item within the iframe anyway to maximize the available area of my external monitor. It is a pain on a desktop but even more so on a laptop.
Surely I'm not the only one experiencing this, so I hope that this could become a checkmark setting on a user level. Better still, it could be scoped per board, so some boards can be actively overviewed with the iframe feature while others are for in-depth work where there's a lot of text, videos, etc.
