I mention these both in the same query because I think this behavior has to do with the way each of them handles master windows, and the concept of "master" in XMonad is something I don't understand very well. The two layouts in particular are:

magnifier = Mag.magnifiercz' 1.3

magnifier $ named "Split" $ combineTwoP (TwoPane (3%100) (2%3)) (noBorders simpleTabbedBottom) (limitWindows 3 $ Column 1) (ClassName "Iceweasel")

and

(magnifier $ gridIM (1%5) (Role "buddy_list"))

With the IM layout, it appears that any new window becomes the master, which is not the desired behavior; the buddy list should stay master, if I understand correctly. The problem with the combineTwoP layout is that one of the iceweasel instances on the left side of the screen is a master window, leading to the undesired behavior of the other one magnifying. Additionally, is it possible to have no master windows (e.g. in a grid layout)? Thank you very much. -- Alex R