- I add the tag "x-window-system" to the list of interesting tags by typing in the box and pressing "Add".
- The tag appears in the list of grey boxes.
- I reload the page.
- The tag "x-window-system" has gone.
Also, there seem to be a lot of equivalent tags, xwindows, x11 and xwindow. The most popular one is "x-window-system" but I can't add that to the interesting tags.