Old topic, I know, but I did a search and this showed up.
I would like to see this feature implemented. Currently using the Feb 11 nightly build and when I close the current tab, the tab to the right is activated. Instead, I would like the previously activated tab to be enabled whenever the current tab is closed.
I have the setting "Use stacked based tab-switching" enabled in the options, and while that changes CTRL+Tab to switch to the previous activated tab, it does nothing when closing the current tab.