I spend a lot of time on, and am a volunteer moderator for, several Stack Exchange sites. (Mi Yodeya is one of them.) SE has a banner ("top bar") that is the same across all sites. It contains notifications, information about the logged-in user, and some key navigation links. For moderators it contains a few more things relevant to that job.
Until recently it looked like this (non-moderator view):
The red counter is the inbox (waiting messages) and the green one is reputation changes. If there aren't any, you just get the gray icons that those alerts are positioned over. If I were a moderator on that site, there'd be a diamond to the left of my user picture and a blue square with the flag count to the left of that.
They've just changed this design. (Well, the change is rolling out.) Here's what it looks like now (for a moderator):
The most important links for moderation are the last two things, the diamond and the blue box with the number (flags). They're on the far right, where they're less likely to be seen for various reasons. (Non-moderators don't get those indicators.)
In the old design, those moderator indicators -- which are important -- were toward the center where they're easier to see. Also, all the numbers were a little bigger and easier to see.
When this was announced there was a lot of immediate discussion in the moderators-only chat room, during which I got a little upset about the reduced usability, especially those moderator controls -- which had a good chance of being scrolled away in a not-huge browser window, because SE doesn't use responsive design. After I calmed down I wrote a post on Meta about how this was going to make it harder for me to do my volunteer job, particularly with vision challenges. I expected to get a few sympathy votes, some "get a bigger monitor" snark (which wouldn't help, by the way), and no results.
That post is now one of my highest-scoring posts on the network. And I have a meeting with the product manager and a designer at SE next week to demonstrate my difficulties in using this in more detail.
Meanwhile, I've gotten some help with userscripts from some other moderators. It's hacky and a little buggy and it slows down page loads and I have no idea how to adjust some things, but at least I can see my notifications and the moderator stuff is in a better place. It'll do for now.
I sure hope I can get them to bake some of this in, though. The page-load delay is a little disconcerting as stuff jumps around on the screen. (Also, userscripts do not work on my Android tablet.)
Beyond the immediate problem, though, what I really hope for is to find some way to raise a little awareness that usability is hard, designers are not the users, there are all kinds of people with all kinds of usage patterns and constraints, and you need to somehow, systematically, figure out how to design for the larger audience. That's going to be the hard part.