So you're on Perlmonks, you've just read a node and want to comment on it. So you click on the associated link and started typing. Do a preview, and continue.
Next you want to insert a quote from the original post, of which the content is no longer visible... what to do? Well: simply duplicate the tab to a new tab or window, which copies the whole history, and go back in that tab... Life can be simple, sometimes.
Niftier still, is the "merge windows" option. Some links do have the tendency to open into a new window. Or, check the home page for an extension. Soon, your screen is littered with browser windows... Just select "merge windows" and the current window disappears, to appear again, with history, into a new tab of an older window. Instant cleanup.
One problem is that the shortcut keys don't work well on other keyboards than QWERTY. The keyboard hook would appear to be lower level than checking the associated Ascii value. On AZERTY, the ctrl-shift-T combination works well, as the T key is in the same spot, but the "M" key isn't, and ctrl-shift-M utterly fails. Oh well. Maybe that'll be fixed in an update.