In D28356#636309, @cblack wrote:

IMO, the maximise and minimise buttons are a step backwards from the current decorations in terms of legibility and aesthetics.
Minimise especially, considering that a square has no meaning at all. Maximise is also less aesthetically pleasing than the current one IMO.

However, I like the new keep below and keep above icons.

I would beg to disagree. After having this for a while on my system I feel the opposite and can't look at the aesthetics of Breeze-Oxygen any more!

The square minimize icon does not mean nothing - it now visually describes what the window looks like once minimized (i.e. compressed), as does maximize (i.e. expanded into a large square).

There is no visual description with the existing arrows which could mean many things. The existing arrows don't have a clear meaning at all - it is not clear whether the down arrow, for example would move the window down, minimize, restore, provide a drop-down menu, scroll etc. As I said in the task, I've seen several users put off KDE just because of the unorthodox nature of Plasma's titlebar buttons.

It has been part of the default kde look for many years (for all of oxygen and breeze) and forms a core part of our design brand. It's something where you can spot breeze on the first look. It seems MacOS can get away with colored circles without people complaining about usability.

I would argue that usability is far more important than branding, and that KDE's brand is not that popular, especially since KDE4 there was a migration away from KDE, coinciding with the Oxygen theme; there are millions of more users that could be migrating to Linux than exist already. The fact that you are on a usable open-source GNU system should sell KDE more than anything! The main thing being imitated here is also KDE1! The arrows in Oxygen/Breeze remind me more of the Windows 3.1 brand and the usability problems I had when I first tried to use it.

I for one would argue that MacOS also does this very badly, and that MacOS usability is not as great as the fanatics would attest.

In D28356#636362, @paulm wrote:

It has been part of the default kde look for many years (for all of oxygen and breeze) and forms a core part of our design brand. It's something where you can spot breeze on the first look. It seems MacOS can get away with colored circles without people complaining about usability.

I would argue that usability is far more important than branding, and that KDE's brand is not that popular, especially since KDE4 there was a migration away from KDE, coinciding with the Oxygen theme; there are millions of more users that could be migrating to Linux than exist already. The fact that you are on a usable open-source GNU system should sell KDE more than anything! The main thing being imitated here is also KDE1! The arrows in Oxygen/Breeze remind me more of the Windows 3.1 brand and the usability problems I had when I first tried to use it.

I for one would argue that MacOS also does this very badly, and that MacOS usability is not as great as the fanatics would attest.

KDE4 was unpopular because it was heavier and buggier, not because the titlebar buttons were different. I didn't like KDE back then either (I mainly used GNOME 2 and Unity), but I did like the window decorations. I think the current buttons are clear enough as they are and any change would be more of a branding change than a usability change. KDE 1 copied a lot from CDE, including the titlebar buttons. Windows 3.1 is different enough that we're pretty obviously not copying it. We also have a maximized symbol, unlike Windows 3.1.

In D28356#636593, @ndavis wrote:

KDE4 was unpopular because it was heavier and buggier, not because the titlebar buttons were different. I didn't like KDE back then either (I mainly used GNOME 2 and Unity), but I did like the window decorations. I think the current buttons are clear enough as they are and any change would be more of a branding change than a usability change. KDE 1 copied a lot from CDE, including the titlebar buttons. Windows 3.1 is different enough that we're pretty obviously not copying it. We also have a maximized symbol, unlike Windows 3.1.

I have been with KDE from the KDE1 days and personally generally liked KDE4 (have never strayed to GNOME :P). I just never liked Windows 3.1's interface nor the Oxygen Windows 3.1-style titlebar buttons (the maximized/restore symbol exists on both and is the same concept - an up arrow fused with a down arrow, though less obvious with Oxygen):

I was also a CDE user on HP-UX back in the day, and think CDE's window controls are no bad thing!

I just think there is a reason why a lot of people are being recommended desktops like Cinnamon, MATE and XFCE etc. to relatives rather than KDE despite Plasma being technically better. It is little things like this where style/branding being prioritised over thinking about how a new user will find intuitiveness/familiarity that is keeping "the year of the Linux desktop" far away!