I may be missing something, but I have not seen a way to sign out of the Micro.blog MacOS app and this has caused some very minor issues as described below.
I went through a phase where I was changing my Micro.blog username relatively frequently. In this situation, all of those names never go away in the upper right drop-down menu of the application.
Even deleting the app and reinstalling it doesn’t remove the old usernames.
You should be able to sign out by choosing File → Sign Out. But that might not help you get rid of the old usernames.
Micro.blog (and most Mac apps, really) leave caches and preference files all over the file system. So dragging the app to the trash is usually not enough to get rid of everything. Doing a quick search, I found the following locations:
./Library/Application Support/Micro.blog/
./Library/Caches/blog.micro.mac/
./Library/HTTPStorages/blog.micro.mac.binarycookies/
./Library/HTTPStorages/blog.micro.mac/
./Library/Preferences/blog.micro.mac.plist
./Library/Saved Application State/blog.micro.mac.savedState/
./Library/WebKit/blog.micro.mac/
There might be more. Deleting all of these directories and files will let you start over fresh with the Micro.blog app. My guess is ./Library/Preferences/blog.micro.mac.plist is the relevant one, so you could try just deleting that first.
To navigate to your Library directory, open Finder and choose Go while holding down the Option key.
If you don’t enjoy finding and deleting those files manually, apps like AppCleaner do it for you.
@sod I just realized I never followed up on this. Your suggestions helped me clear it up. Thank you.