Occasionally GMs must contact players, whether through tells or through shouts. The former is typically for a good reason, the latter is generally for a server reset or other important server-wide information....which is also a good reason. It is somewhat frustrating when people play with their chat windows minimized or hidden such that such we have to take extra steps to contact them and/or break immersion for them and those around them.
I realize that screen real estate for some may be more limited than others, but I do humbly request that these windows stay open and visible during game play.