Season of Discovery Phase 4 introduced some unexpected changes. One of the most controversial changes was updating the Guild panel to match its Retail counterpart. This change is likely a part of the continued effort to unify the multiple clients Blizzard now has to work with, but there has been no official statement yet. While most players reacted indifferently to this change, there was some outcry on various forums.
While many players have called this the «Cata UI», that statement isn't true. The original Cataclysm Guild panel was much closer to the original panel than the Retail panel, being contained to one single-width window while covering parts that didn't make it into Cataclysm Classic, such as Guild Levels.
The first and most obvious difference is that the overhauled panel is twice the width of the original. This allows more information to be visible while removing the necessity for the big yellow arrow to swap from ranks and notes to classes and levels. The downside is that the panel obscures a large amount of the screen whenever it is open. At higher resolutions and adjusted UI scale settings, this will likely cover a little less than half your monitor's width.
Despite the increased size, some information that was always visible is now in a separate tab. The guild message of the day is relegated to the «Info» tab, together with Guild Information and a new addition, Guild News. Something that was brought up in the initial discussions was the swap from class names displayed as text over to class icons. Players that used ElvUI will likely not have noticed a difference here, as ElvUI already changed that particular element.
A large amount of space on the new panel is also dedicated to separate communities. Unfortunately, this function is not available in Season of Discovery, meaning this is instead wasted space. The new «Note» section also has a habit of truncating text that could have easily fit. Despite the obvious minimize arrow in