Do you have AB+ or Repentance?
The folder where mods are installed varies between these DLCs:

Repentance:
C:\Program Files (x86)\Steam\steamapps\common\The Binding of Isaac Rebirth\mods\

Afterbirth+:
C:\Users\[username]\Documents\My Games\Binding of Isaac Afterbirth+ Mods\

To successfully hard uninstall a mod, you need to unsubscribe from it AND delete the folder of the mod from the Mods folder. Then start the game to let it clean up its cache.
Then close game and subscribe to the mod again. This should definetly install the mod correctly.
If all that still doesnt help, please install the mod manually like this:

1. Download the most recent version of the mod: https://github.com/wofsauge/External-Item-Descriptions/releases
2. Extract the content of the "external.item.descriptions.zip" file
3. Put the folder "external item descriptions" into your mods folder like this:
Repentance: ..\steamapps\common\The Binding of Isaac Rebirth\mods\external item descriptions\
Afterbirth+: ..\Documents\My Games\Binding of Isaac Afterbirth+ Mods\external item descriptions\
4. Start the game

After a manual install, it's working and even has the smaller font I set previously. It also has the proper "!!~External item descriptions" name in the mod menu instead of "External item decriptions_8363something". I'm guessing the non-workshop version won't update itself so I'll have to manually go to the github page every time there's an update? Kinda sucks, but I can deal with it.