Are you referring to the Description field or Additional Properties? If you're talking about the properties, I noticed this too (assuming you're talking about the value field of a property in a credential) and I think it's a 6.5 thing because I didn't notice this is 6.4. But the value you input there is still saved. It just doesn't display at all in the UI. In 6.4, I feel like I remember it being just like a password field where it is masked in the UI but it still gave an indication that a value was entered there.
I currently use additional properties of credentials in 6.5, so I can confirm that it doesn't affect functionality.
Edit: I swear. Every time I try to read a forum post late in the day, it's like my eyes don't work. I see now that you literally said 'Additional Properties'. lol
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Dave Morris
3Ci @ Southern Company
Atlanta, GA
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Dave Morris, 3Ci at Southern Company