I appreciate that you included the design pitches. They show the process focused on making the logo work for the individual sites:
At full size the two designs are clearly different. They share design sensibilities, which I think can be attributed to two things:
Despite many differences between Stack Exchange communities, all our sites share many common values and customs.
Both designs were created by Stéphane.
I talked to Stéphane yesterday to gather information to write an answer to a related question on Meta Puzzling. He's comfortable with both designs as is. However, I think the smallest logos are a bit too similar as favicons and on the Hot Network Question sidebar. The problem is not unique to this pair of logos, so I proposed a general solution for the sidebar: append the name of each site to the logo. From the feedback I've received so far, it sounds like that suggestion does not cover most (if any) of the concerns of The Workplace community.
Stack Exchange has always valued community input when it comes to site design. In fact, the original logos for Stack Overflow, Server Fault and Super User were designed by users. Even today, our professional designers solicit community feedback. As recently as the Emacs design you can see that they sometimes change the entire concept of the logo in response to community concerns.
The deeper issue seems to be that The Workplace community didn't follow the design process on Puzzling and only noticed the problem when the design had been finalized. Unfortunately, the way most people initially encounter new site logos is on the Hot Network Question list, which is a feature already disliked by many. So I definitely understand the frustration this community has had with the situation. It's not a pleasant surprise to click on a link that you thought might be some hot new question on your favorite site and land on a question intentionally designed to be cryptic. I would go so far as to call it clickbaity.
Again, fixing the sidebar to remove surprise solves only part of the problem. It does not address the deeper concern:
I think what bothers me (and probably others) most is that this design decision affects us at the Workplace, but we had no say in the matter. In the real world you obviously can't expect this, but we are a closed community with common oversight. We shouldn't all be involved in site-specific decisions, but I would expect those who approve such changes to consider how it may affect others in the greater SE community. I don't feel like that happened here. – David K
As a matter of fact, the similarity was noticed back when the logo was first revealed. If I had to characterize the feedback for the logo in particular, I'd call it "mixed". So the logo should have been changed, right? Not so fast. Every design pitch meets resistance because people have a picture in mind that is very likely different than the designer's. (From my experience as a user: I didn't much like the Christianity deisgn when I saw it. It's grown on me.) Part of the designer's job to have the courage of conviction to stick to their guns sometimes.
My thoughts can be summed up by this comment:
The case of the perfect Puzzling SE logo might be unsolvable. Many SE logos are already enigmatic and all of SE is built on the question mark. At sizes usually displayed, SE logos pretty much amount to shapes and shades -- check out the color-bordered diamond of workplace.stackexchange.com – humn
I can see an argument for building a "logo conflict" check into our process. That might even result in better, more distinct logos. But in this case, that hypothetical process would not have changed the end result.