[megous]

That only applies when you open a tab by clicking on a link. If you do ctrl+t, you'll get new tab at the far right.

[the_duke]

That is toggled by "browser.tabs.insertAfterContent" ( vs insertRelatedAfterContent).

[lorenzhs]

You have a typo there, it's browser.tabs.insertAfterCurrent and browser.tabs.insertRelatedAfterCurrent (Current, not Content), just in case someone tries to copy and paste those into about:config

[nabergh]

This is correct and it also applies when middle clicking a link. That's where it really matters for me.