My fix for weird title bar issue / error
I too had this issue, and it looks like this is the only place people are talking about it, so I thought I'd share my solution.
Although I fixed it without reinstalling, and despite my thorough, systematic approach, I wasn't able to figure out the exact cause.
Here's what I did to get around this issue (I'll try to remember exactly what I did, feel free to ask if it doesn't work for you, or if my steps don't make sense) I'm sorry if this is a rushed how-to, I already spent a lot of time fixing it on my own machine:
What we're going to do here is make a new, clean user Library folder, then start moving all your Library files back into it until you're done, or until you find the cause of the weird title bar issue (again, I fixed it on my machine, but I'm not sure what started it all. The only file I didnt copy over was ~/Library/Preferences folder/com.apple.scheduler.plist, because it gave me an invisible file warning. Maybe this was the cause? Opened it up and saw nothing in it that I would think could cause this problem. I have a feeling the cause is something inside the ~/Library/Preferences folder).
1: Create another Admin account (I used my girlfriend's account, as it was already an Admin).
It'll be easier if, while creating this new Admin, you sign in with the iCloud of the account you're trying to fix.
Also, you may have to add your new Admin with full read/write privileges to your original user Library's "Sharing and Permissions" section in the Finder's info panel. Make sure you "Apply to enclosed items" under the little gear / triangle option at the bottom of the "Sharing and Permissions" section.
2: Turn on fast user switching so you can switch in and out of your old and new accounts to see if the problem comes back during the next few steps.
3: Rename your user Library LibraryOLD (or whatever youd like).
4: Copy your new Admin account's library folder into the home folder of the account youre trying to fix (make sure to copy, not move). This will give you a starting point with a Library that isn't effected by this "bug".
Also, similar to the end of step 1, you should probably add your original account to this new copied Library's "Sharing and Permissions" section, give it full read/write status, and "Apply to enclosed items".
5: Open your old user Library folder ("LibraryOLD") in a Finder window, and open the new Library folder in a 2nd window.
6: Select everything in the old Library and label it a color (I used Purple) by right clicking and choosing a color circle, so you can keep track of the files you move in the next step.
7: Start moving (not copy) your old Library files/folders to the newly created Library, maybe in batches of 20 files/folder at a time. After each batch switch to your original user account via the Fast User Switch menu item in the menu bar. Be sure to log out of the original user account after each check to be sure its reading the next batch of Library files correctly. For each batch of files/folders you know are good, set their label color to nothing (right clicking and choosing the x).
8: Once you get through all your files, your original user account should back to its old self, without this annoying issue. If you figure out what the file is, please let me / us know. I have a feeling its in the ~/Library/Preferences folder, so you may want to save that folder for the end, and do step 7 to the contents of the Preferences folder, instead of copying it over in one whole shot.
Good luck!